System and method for automated perfusion measurement

Abstract

Systems and methods for automated perfusion measurement are provided. The present disclosure relates to a system and method for automatically measuring and assessing hemodynamics in tissue of a subject's anatomy. In particular, the present disclosure relates to continuous measurement and assessment of hemodynamics in a medical procedure using fluorescence imaging, and wherein the administration of fluorescent agents is controlled and automatic. One aspect relates to a system for automatic perfusion assessment of an anatomical structure during a medical procedure of a subject, the system comprising a controllable injection pump for containing at least one first fluorescent imaging agent, the injection pump configured for injecting a predefined amount of said first fluorescent imaging agent into blood of the subject, wherein the system is configured to receive and analyze a time series fluorescence image of tissue of the anatomical structure after injection of the first fluorescence imaging agent, and determine at least one perfusion parameter of the anatomical structure based on the analysis.

Description

[0001] This application is a divisional application of the application with the filing date of June 14, 2019, application number 201980053515.9, and invention title "System and method for automatic perfusion measurement". Technical Field

[0002] The present disclosure relates to a system and method for automatically measuring and evaluating hemodynamics in the tissue of an anatomical structure of a subject. In particular, the present disclosure relates to the continuous measurement and evaluation of hemodynamics during a medical procedure using fluorescence imaging, and wherein the administration of the fluorophore is controlled and automatic. Background of the Invention

[0004] Fluorescent imaging agents (also referred to as fluorescent contrast agents, also referred to as fluorophores, such as indocyanine green (ICG)) have been introduced many years ago to visualize blood flow and perfusion in anatomical structures, but the clinical application of this technique has been rare. Currently, the dose of the fluorophore must be large enough to ensure that the visual signal is strong enough to be easily detected by the surgeon. Therefore, the assessment of perfusion in tissue based on the fluorophore is based on the visual inspection of the surgeon, i.e., it is largely subjective and may vary from surgeon to surgeon. An improved quantitative analysis method for perfusion assessment in the gastrointestinal tract is disclosed in the pending application PCT / EP2017 / 082204, titled "System and method for assessing perfusion in an anatomical structure", published as WO 2018 / 104552 by the same inventors. This application is incorporated herein by reference in its entirety.

[0005] Existing fluorescence imaging methods are typically based on very few perfusion measurements, perhaps only one, performed only at key points during a medical procedure, such as before bowel resection and after formation of a bowel anastomosis. To form a fluorescent signal visible to the surgeon (or other medical professional), a large dose of the fluorophore is required. Such a large dose results in a burst of visible fluorescence emission, but the washout period may be 20 - 30 minutes, during which the fluorophore is still in the patient's blood, generating a visible background fluorescence emission signal. During the washout period of removing the fluorophore from the blood, this visible fluorescence emission signal will typically prevent medical staff from initiating new fluorescence measurements during the washout period.

[0006] Today, measurements using fluorescence imaging involve many manual steps, during which the entire operating room is "paused" for several minutes. It is usually the surgeon who decides to perform a measurement involving fluorescence imaging, such as evaluating perfusion in the tissue of an anatomical structure. Initially, the surgeon correctly positions the anatomical area of interest in the video image received from a white light camera (such as an endoscopic camera). Then, the surgeon switches the normal white light to another camera that can capture the fluorescence emitted from the area of interest, and then the surgeon prompts the assistant to inject a fluorescent agent into a surrounding vein. After waiting about 30 seconds, the first fluorescence emission signal will appear, and the surgeon waits for several minutes until it is determined that the visible fluorescence signal has been adequately evaluated. Summary of the Invention

[0007] The manual implementation and evaluation of fluorescence imaging, combined with only discrete measurements and a long washout period, constitute a significant practical limitation in the use of fluorescence image perfusion analysis in elective and emergency procedures. During emergency procedures, it is crucial not to perform greater surgical interventions unless necessary, as this increases the surgical time and postoperative morbidity. At the same time, the surgeon cannot afford to leave an intestinal organ or part with insufficient perfusion, which may lead to tissue ischemia, necrosis, infection, anastomotic leakage, and even death [Lioit et al. 2018]. Therefore, an object of the present invention is to make fluorescence imaging more easily integrated during emergency procedures.

[0008] Accordingly, in a first embodiment, the present disclosure relates to a system for automatically evaluating the perfusion of an anatomical structure of a subject, for example, during a medical procedure such as surgery. The system can be configured to control the injection of a predefined amount of a fluorescence imaging agent into the blood of the subject. The injection can be provided by a controllable injection pump, which can be under the control of the system. The injection pump can be part of the system, and the system includes at least one controllable injection pump for containing at least one fluorescence imaging agent. That is, the injection pump can be configured to inject a predefined amount of the fluorescence imaging agent into the blood of the subject. Preferably, the system is configured such that a predefined amount of the fluorescence imaging agent can be repeatedly injected at regular and / or predefined intervals. The system can further be configured to receive and analyze time-series fluorescence images (also called video images) of the tissue of the anatomical structure after injecting the fluorescence imaging agent. Based on this analysis, at least one perfusion parameter of the anatomical structure can be determined.

[0009] In one embodiment, the present disclosure relates to a system for automatically assessing perfusion of an anatomical structure during a medical procedure on a subject, the system including a controllable injection pump for containing at least one first fluorescent imaging agent, the injection pump being configured to inject a bolus corresponding to a predefined amount of the first fluorescent imaging agent into a vein of the subject, wherein the system is configured to receive and analyze time series fluorescence images of tissue of the anatomical structure after injecting the first fluorescent imaging agent and determine at least one perfusion parameter of the anatomical structure based on the analysis.

[0010] In one embodiment, the bolus corresponds to a first fluorescent imaging agent of less than 0.01 mg ICG / kg body weight. In one embodiment, the bolus corresponds to a first fluorescent imaging agent of less than 0.5 mg ICG. In one embodiment, the bolus corresponds to a first fluorescent imaging agent of less than 0.5 mg ICG.

[0011] In one embodiment, the fluorescent agent is ICG, and wherein the amount of ICG in the bolus is less than 0.01 mg / kg body weight. In one embodiment, the fluorescent agent is ICG, and wherein the amount of ICG in the bolus is less than 1 mg ICG or less than 0.5 mg ICG.

[0012] In one embodiment, the system is configured to inject the bolus at intervals between 5 and 600 seconds, such as between 15 and 300 seconds, such as between 45 and 210 seconds, such as between 90 and 120 seconds.

[0013] In one embodiment, the system is configured to determine a subject-specific minimum effective bolus of the fluorescent imaging agent by the following steps:

[0014] - Controlling the injection pump to inject a series of boluses of the fluorescent imaging agent with varying amounts, with a predefined time period between each bolus,

[0015] - Analyzing the fluorescence emission of the anatomical structure after injecting each bolus, and

[0016] - Determining the size of the minimum bolus that provides quantifiable fluorescence emission from the anatomical structure.

[0017] In one embodiment, the quantifiable fluorescence emission of the anatomical structure corresponds to the fluorescence emission from which a perfusion slope can be determined.

[0018] In one embodiment, the system is configured to determine a subject-specific interruption interval, the subject-specific interruption interval being defined as the time period from when the fluorescence slope rises to when the fluorescence emission drops below a multiple of the standard deviation of the background noise, such as 20, 10, or 5 standard deviations.

[0019] In one embodiment, the system is configured to automatically: 1) control an injection pump to inject a series of predefined boluses of a fluorescent imaging agent, such as a minimum effective bolus, with a predefined duration between each bolus, and 2) determine at least one perfusion parameter of the anatomical structure after each bolus injection.

[0020] In one embodiment, the system is configured to automatically: 1) control an injection pump to inject a series of boluses of a fluorescent imaging agent with varying amounts, with a predefined time period between each bolus; and 2) determine at least one perfusion parameter of the anatomical structure after each bolus injection.

[0021] In one embodiment, the system is configured to accommodate at least a second fluorescent agent, different from the first fluorescent agent, and wherein the system is configured to inject one or more boluses of the second fluorescent imaging agent with a predefined amount into the bloodstream of a subject.

[0022] In one embodiment, the system is configured to determine the at least one perfusion parameter in one or more regions of interest located in the anatomical structure and optionally in adjacent anatomical structures, and wherein the regions of interest can optionally be selected by a user of the system.

[0023] In one embodiment, the system further includes at least one light source configured to provide excitation light to induce fluorescence emission from the first and / or second fluorescent agent in the anatomical structure; and an imaging unit configured to record the time series of the fluorescence emission from the anatomical structure.

[0024] In one embodiment, the system is further configured to track the movement of at least a sub - part of the anatomical structure in the time - series images, and in relation to the movement, such that at least the first region of interest corresponds to the same sub - part of the anatomical structure in the image, and wherein the movement tracking is provided by free - image tracking and / or by object - based tracking.

[0025] By automating fluorescence perfusion assessment, we reduce the time that surgeons and the rest of the operating room staff must be idle. Automation of fluorescent agent administration can further increase the use of fluorescence imaging, making perfusion assessment easier. This may lead to modifications in surgical strategies, such as creating a larger resection, or performing a resection when none was planned, or even starting a planned resection but not removing it all together.

[0026] In an emergency situation, the surgical time is a limiting factor. Compared with elective surgery, the surgical plan will generally be more unplanned. During such an emergency procedure, multiple perfusion assessments of the same or different tissues may be required within a short period of time. Although a single perfusion measurement can be performed within a reasonable time, multiple measurements will rapidly extend the surgical time and become infeasible. This is an obstacle and the reason why these measurements are still not routinely used.

[0027] Accordingly, the system disclosed in the present application can be further configured to control an injection pump to inject an initial small bolus of a fluorescent imaging agent and then analyze the fluorescence emission generated by the initial bolus. The initial small bolus, preferably in combination with a saline solution flush, should be selected depending on the circumstances, i.e., which type of fluorescent agent is used and the patient configuration, such as age, weight, height, etc. However, an amount less than 0.01 mg / kg of the subject's body weight (i.e., less than 0.5 mg for a 50 kg patient and less than 1 mg for a 100 kg patient) is generally a good starting point, especially when using ICG.

[0028] The inventors have recognized that, for example, through the use of computer image analysis, the quantifiable fluorescence emission from tissues of anatomical structures is much less than the fluorescence emission visible to the human eye. That is, much smaller doses, such as microdoses, are possible because the fluorescence signal intensity only needs to be large enough to be measurable by computer vision and image analysis without the need for visual inspection by a surgeon. That is, a microdose of a fluorescent agent can be administered to a subject, and perfusion parameters can be determined therefrom, for example.

[0029] The minimum bolus providing quantifiable fluorescence emission can be estimated depending on the circumstances. However, to find a more precise minimum effective bolus, the system disclosed in the present application can be further configured to determine a subject-specific minimum effective bolus of a fluorescent imaging agent by the following steps: controlling the injection pump to inject a series of boluses of the fluorescent imaging agent with varying amounts according to a predefined criterion (such as increasing or decreasing), with a predefined time period between each bolus, analyzing the fluorescence emission of the anatomical structure after injecting each bolus, and determining the size of the minimum effective bolus that provides quantifiable fluorescence emission from the anatomical structure.

[0030] By applying a microdose of a fluorescent agent, the shortest time between consecutive measurements can be significantly reduced. Moreover, by determining the actual subject-specific minimum bolus that provides quantifiable fluorescence emission, a shortest washout period is also ensured, which can minimize the duration between consecutive fluorescence measurements. This is because smaller doses can be removed from the blood more quickly.

[0031] Once a suitable bolus size that provides a quantifiable fluorescence signal and a short washout period that allows for repeated injection of the fluorescence imaging agent and fluorescence measurements have been found, the system can be configured to perform automated measurements of perfusion parameters, e.g., at a predefined frequency determined by the washout period. Thus, the system disclosed in the present application can be further configured to automatically: 1) control an injection pump to inject a predefined bolus of a series of fluorescence imaging agents, a predefined bolus such as a minimum effective bolus, with a predefined time period between each bolus, and 2) determine at least one perfusion parameter of the anatomical structure after injecting each bolus.

[0032] Now, provide continuous perfusion assessment of the anatomical structure for surgeons and other medical professionals in the operating room. Thus, the systems and methods disclosed in the present application open up the possibility of providing continuous fluorescence imaging measurements, which can provide a series of perfusion parameters as a kind of background information during a medical procedure. That is, even if the surgeon has switched back to white light imaging during an actual surgical procedure, the fluorescence measurements can still be automatically performed in the background without manual intervention. Thus, valuable information about perfusion can be continuously provided to medical staff in a time perspective, because repeated perfusion measurements provide the possibility of tracking the development of perfusion parameters over time. Therefore, the use of automation and microdosing in fluorescence perfusion measurements will open up a series of entirely new applications, including regular use in emergency and elective procedures to continuously assess the viability of tissues and organs (such as the thyroid and parathyroid glands, hepatobiliary ducts, reproductive organs, and bladder); tumors and their localization, including lymph nodes and possible metastases; and assessment of skin / tissue / vascular perfusion in various medical procedures, such as assessment of wounds and wound healing.

[0033] When measuring fluorescence perfusion in a traditional way, i.e., performing a single measurement at one or more different points during the surgery, the measurement will always be sensitive to measurement "noise". The automation of fluorescence perfusion measurements and the reduction of the minimum interval between consecutive measurements make it more feasible to perform multiple measurements on the same area of interest during a medical procedure. Providing multiple measurements is a great advantage because it reduces the influence of random noise caused by the random diffusion of the fluorophore, physiological changes in blood flow, and distribution in the microcirculation of any anatomical area. Overall multiple measurements on the same area of interest result in a better and physiologically correct perfusion assessment.

[0034] If the surgeon wishes, the surgeon can still perform and save "normal" / full-dose fluorescence perfusion measurements, providing a visual signal at key points during the surgical procedure. These can, for example, be used as documentation of the quality of the procedure in the electronic medical record. After planning the first measurement, the surgeon can continue the medical procedure with minimal interruption to understand the input perfusion values or change the area under continuous assessment.

[0035] The inventors further recognize that the measurement and analysis of repeat bolus injections can additionally be extended from the interpretation and quantification of single inflow and / or single outflow phases to the analysis of oscillatory fluorescence kinetics. These oscillatory fluorescence kinetics can reveal hitherto unobtained physical perfusion characteristics without invasive measures.

[0036] The systems and methods disclosed herein can be configured to repeatedly inject small boluses at regular intervals, such as the minimal boluses disclosed herein. These boluses can result in periodic variations depending, for example, on the injection time interval, which, when measured, approximate the form of an oscillatory curve, such as a regular oscillatory curve, such as a sine curve. In such a curve, it is expected that the measured intensity signal increases as the fluorescent imaging agent flows in from a given bolus and then decreases during the washout period of the bolus until it increases again at the subsequent bolus, and so on, resulting in a periodic (sine) pattern.

[0037] Accordingly, the present disclosure also relates to a (computer-implemented) method for detecting perfusion changes in a region of interest of a subject by performing image processing on the hemodynamics in at least a portion of the region of interest in video images obtained from the subject. In one embodiment, the method includes the steps of performing image analysis on at least one video sequence obtained during and / or after supplying a plurality of boluses containing a fluorescent imaging agent to the subject. In that case, it is advantageous if the plurality of boluses are provided according to a predefined pattern, for example in terms of frequency and / or dose, which is also elaborated further in the present disclosure. One or more subsequent perfusion parameters in the region of interest can now be calculated based on the image analysis, i.e., when a plurality of doses are administered to the subject, the perfusion parameters can be calculated continuously as the boluses are provided. By utilizing the variation of the provided plurality of perfusion parameters over time (and bolus administration), it becomes possible to monitor the subsequent perfusion parameters to determine perfusion changes in the region of interest. Such changes in perfusion may indicate a problem.

[0038] Preferably, the system disclosed in the present application is configured such that it can identify the parameters of the oscillation intensity curve, such as frequency, phase, and / or amplitude. Then, the trained system can in turn predict the direction and regularity of the upcoming signal dynamics. The system preferably uses the measured values to identify the oscillation pattern, such that the system can thereafter detect the difference between the measured values and the expected values. The system does not necessarily have to continuously measure the anatomical region of interest. Instead, it can only be capable of making measurements at sporadic time intervals, for example, in the case where the anatomical region of interest drifts in and out of the focus of the recorded image. In these cases, the expected phase of the oscillation pattern at the measured time intervals can be compared with the measured phase. The measured values can be further continuously used to update the detected pattern, i.e., the expected values. Alternatively or additionally, injection parameters such as bolus frequency, dose, and flow rate can be used to determine the expected values, i.e., the oscillation pattern.

[0039] The difference from the expected sinusoidal pattern may be caused by, for example, the onset of an ischemic condition in at least a part of the anatomical structure visible in the video image, or a regional change in the perfusion into a given area. In Figure 12A illustrative figures are given that demonstrate such kinetic changes due to an ischemic episode in a human subject, and in Figure 12B a zoomed-in view of a narrower range is given. As can be seen, a transition from a regular oscillating fluorescence signal to an ischemic flatline can be detected. However, it should be noted that changes in the perfusion of the anatomical structure of interest can result in measured patterns other than an ischemic flatline. An example is venous occlusion, where the outflow of blood from the anatomical region is blocked or reduced due to congestion or accumulation of the fluorophore in a given area, resulting in changes in the oscillatory dynamics. As can be seen from Figure 13C although the periodic oscillations stop, the result is not a flatline.

[0040] Preferably, the system disclosed in the present application includes a tracking device and is capable of running independently in the background, while the surgeon is only exposed to the visible white light signal and is thus only interrupted / notified by a warning signal, for example, during the detection of an ischemic episode, which can be defined by an extended amount of time in an ischemic condition.

[0041] Following the above disclosure, the present disclosure also relates to a method for automatically assessing the perfusion of a subject's anatomical structure, the method including intravenously administering a bolus agent that is about 1 / 10 of the normal dose for perfusion assessment. For indocyanine green (ICG), the normal bolus agent is 0.1 - 0.3 mg / kg body weight. According to the present disclosure, a bolus agent of less than 0.01 mg / kg body weight of the first fluorescent imaging agent can be used. For other fluorescent imaging agents described herein, the bolus agent is similarly reduced according to the present disclosure.

[0042] In one embodiment, the present disclosure also relates to a method for automatically perfusing and evaluating the anatomical structure of a subject, the method comprising intravenously administering a bolus corresponding to a first fluorescent imaging agent of less than 0.01 mg ICG / kg body weight, acquiring and analyzing time-series fluorescence images of the tissue of the anatomical structure after injecting the first fluorescent imaging agent, and determining at least one perfusion parameter of the anatomical structure based on the analysis.

[0043] In one embodiment, the agent is injected by a controlled infusion pump. In one embodiment, the agent is injected in a series of boluses with a predefined time between subsequent boluses.

[0044] In one embodiment, the fluorescence emission of the anatomical structure is measured after injecting each bolus.

[0045] In one embodiment, the bolus comprises an increasing or decreasing amount of the agent. In one embodiment, the amount increases or decreases from one bolus to the subsequent bolus in 10% increments.

[0046] In one embodiment, the minimum bolus is determined after administering a series of increasing or decreasing boluses, the minimum bolus providing a quantifiable fluorescence emission representative of the perfusion of the anatomical structure.

[0047] In one embodiment, the interval between boluses is between 5 and 600 seconds, such as between 15 and 300 seconds, such as between 45 and 210 seconds, such as between 90 and 120 seconds.

[0048] In one embodiment, the interval between boluses is long enough to allow measurement of the perfusion slope of each bolus in the anatomical structure, preferably, wherein the perfusion slope includes a slope start point and an elution slope.

[0049] In one embodiment, a volume of isotonic solution (such as saline) is immediately injected after injecting the fluorescent imaging agent of the bolus, for example, wherein the volume is 1 - 20 mL, such as 2.5 - 15 mL, such as 5 - 10 mL.

[0050] In one embodiment, the amount of the fluorescent imaging agent corresponds to 0.001 to 0.01 mg ICG / kg body weight per bolus, such as 0.001 to 0.01 mg ICG / kg body weight per bolus.

[0051] In one embodiment, the initial amount of the fluorescent imaging agent corresponds to at least 0.001 mg ICG / kg body weight.

[0052] In one embodiment, subsequent boluses increase or decrease from one bolus to the subsequent bolus corresponding to at least 0.001 mg ICG / kg body weight.

[0053] In one embodiment, the bolus has a liquid volume of from 0.5 μL to 10 mL, such as 0.5 - 5 mL.

[0054] In one embodiment, a second fluorescent imaging agent is administered, the emission maximum of which differs from the emission maximum of the first fluorescent imaging agent by at least 50 nm.

[0055] In one embodiment, the present disclosure also relates to a computer - implemented method for detecting perfusion changes in a region of interest of a subject by hemodynamics in at least a portion of the region of interest of the video image obtained from the subject by image processing, the method comprising the steps of:

[0056] - Performing image analysis on at least one video sequence obtained during and / or after supplying a plurality of boluses containing a fluorescent imaging agent to the subject, wherein the plurality of boluses are supplied according to a predefined pattern, such as in terms of frequency and / or dose.

[0057] - Calculating subsequent perfusion parameters of one or more regions of interest based on the image analysis, and

[0058] - Monitoring the subsequent perfusion parameters to determine changes in perfusion in the region of interest.

[0059] In one embodiment, the method further comprises the steps described in any of the preceding items. For example, the systems and methods disclosed in the present application can be used, where during surgery, i.e., in the field of visceral surgery such as left colon and rectal resection, gastric slice displacement after esophagectomy, free small intestine transplantation for insertion and anastomosis, etc., quantifying the circulation through tissues can play a decisive role. The methods disclosed in the present application can also be applied to detect secondary perfusion abnormalities in cases of strangulated hernia or bridenileus. In cardiac surgery, the systems and methods disclosed in the present application can be used to examine the efficiency of coronary artery bypass grafting and measure perfusion during surgery. In the field of plastic surgery, the perfusion of transplanted skin flaps can be (e.g., continuously) monitored, and tissue damage can be evaluated in case of trauma, as well as wound healing (e.g., chronic wounds) can be evaluated.

[0060] Another aspect of the present disclosure relates to continuous perfusion assessment related to repeated injections of a fluorescent active agent and monitoring of the resulting oscillatory curves. In addition to detecting unforeseen perfusion changes, the system can also be used to evaluate the perfusion area of an artery. For example, a surgeon may consider incising an artery as part of a surgical procedure. Before incising the artery, the surgeon can temporarily restrict the perfusion through the artery, and the methods disclosed in this application can enable visualization of the perfusion area of the artery within a short period of time (e.g., less than 1 minute). This can be valuable information for a surgeon during a continuous surgical procedure. In a similar manner, the system can be used to evaluate the drainage area of a vein or a group of veins, lymphatic vessels, lymph nodes, or other parts of the circulatory and / or lymphatic pathways. By temporarily restricting blood flow through a blood vessel, blood will accumulate in the anatomical area normally drained by that blood vessel or that group of blood vessels. This enables visualization of the anatomical area drained by the blood vessel within a relatively short period of time (e.g., less than 2 minutes). This can provide important information to a surgeon in fields such as general surgery and plastic surgery (including wound and reconstructive surgery), for example, during a continuous surgical procedure.

[0061] Another aspect of the present disclosure relates to a computer program, such as a computer program recorded on a storage medium, which will be loaded into the memory of a computer or the system disclosed herein, and the program causes the computer / system to perform the steps of any of the methods disclosed herein.

[0062] Another aspect of the present disclosure relates to an imaging system, namely an endoscopic imaging system, which includes a processing unit configured to perform the steps of any of the methods disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1A 、 1C and 1E show embodiments of the intensity curve after an ICG bolus is provided to a subject, Figure 1B 、 1D and 1F show the corresponding intensity curves, in which the hemodynamic parameters perfusion slope, slope start point, slope end point, maximum intensity, washout slope, washout start point, and washout slope end point have been calculated and shown in the figures.

[0064] Figures 2A - 2F show three embodiments that show the method disclosed herein for determining the time point at which the perfusion slope starts (i.e., the slope start point). Figure 2B 、 2D and 2F are close-ups of Figure 2A 、 2C and 2E, respectively, where the slope starts.

[0065] Figures 3A - 3FThree embodiments are shown that illustrate the method for determining a perfusion slope based on histogram data disclosed herein.

[0066] Figures 4A - 4F Three embodiments are shown that illustrate the method for defining and determining a maximum slope intensity disclosed herein. Figure 4B 、 4D and 4F are close-ups of Figure 4A 、 4C and 4E, respectively, where the curve has its maximum intensity.

[0067] Figures 5A - 5F Three embodiments are shown that illustrate the method for analyzing the washout of a fluorescent contrast agent disclosed herein. Figure 5B 、 5D and 5F are close-ups of Figure 5A 、 5C and 5E, respectively, where ICG is washed out.

[0068] Figures 6A - 6D Two additional fluorescence measurements using ICG are shown, demonstrating the robustness of the analysis method disclosed herein.

[0069] Figure 7 Output video frames obtained during intestinal surgery are shown, along with four different regions of interest and their analysis.

[0070] Figure 8A A still image of a normal video sequence obtained prior to resection of a patient's colon is shown. The image shows the small intestine (lower) and colon (upper).

[0071] Figure 8B Shows a fluorescence image of a gastrointestinal subpart that is substantially the same as in Figure 8A but obtained later (i.e., after a bolus injection of a fluorescent contrast agent (ICQ) has been administered to the patient).

[0072] Figure 9A Shows the intensity curve obtained in the ROI of Figure 8B and the perfusion slope calculated according to the method disclosed herein, i.e., the perfusion slope of the colon and small intestine prior to resection.

[0073] Figure 9B Shows Figure 9A the perfusion slopes of the small intestine (left) and colon (right) in Figure 9B but in

[0074] Figure 10A Shows a normal image of a gastrointestinal subpart that is substantially the same as in Figure 8A but obtained after resection of the colon and prior to anastomosis.

[0075] Figure 10B It is a fluorescence image corresponding to the image in Figure 10A after an ICG bolus has been injected. Five ROIs are shown in the image.

[0076] Figure 11A Shows the intensity curves measured by Figure 10A and 10B as shown.

[0077] Figure 11B Shows Figure 11A the perfusion slopes of the small intestine (left) and colon (right, blue, green, and yellow) in Figure 11B but here in

[0078] Figure 12A Shows the oscillatory time-intensity fluorescence curve, where the oscillation is disrupted due to an ischemic episode in a human subject.

[0079] Figure 12B Shows an enlarged view of the time interval near t = 3800 s in the previous figure, where an ischemic episode occurred.

[0080] Figure 12C Shows idealized data with and without an ischemic condition.

[0081] Figure 12D Shows idealized data where only a part of the oscillatory time-intensity fluorescence curve can be detected.

[0082] Figure 13A Shows consecutive measurements in a human subject injected with a micro-bolus.

[0083] Figure 13B Shows Figure 13A an enlarged view of the interval shown.

[0084] Figure 13C Shows the measurement results of a person subjected to venous occlusion, where blood flow is only partially restricted. DETAILED DESCRIPTION OF THE INVENTION

[0086] To determine a subject-specific minimum effective bolus, it can be advantageous to determine a background level of the setup, such that a minimum quantifiable fluorescence signal can be determined. Thus, the system disclosed in the present application is advantageously configured to: 1) receive time series images of the tissue of the anatomical structure before injection of the fluorophore, and 2) determine a background noise level therefrom. Before or after this, one or more regions of interest (ROIs) can be selected. This selection of ROIs can be provided manually by the user, automatically by the system, or semi-automatically, where the system suggests a plurality of ROIs and the user can edit and / or move the suggested ROIs accordingly. A background noise level can be determined for each ROI.

[0087] As previously mentioned, a minimum effective bolus can be determined, in particular a subject-specific minimum effective bolus. The size of the minimum effective bolus can be determined, for example, based on the background noise level, in particular according to the standard deviation of the background noise level. For example, the minimum effective bolus can be determined as the bolus providing the maximum intensity, which is a predefined coefficient multiplied by the standard deviation of the background noise level. We note that the intensity of the background noise level can be close to zero or can not be close to zero. The background noise can also vary (e.g., due to a long series of microboluses). However, the variation of the background noise preferably occurs on a much larger time scale, e.g., at least 2 times larger, more preferably at least 4 times larger, even more preferably at least 6 times larger, and most preferably at least 10 times larger than the intensity variation observed for a single injection.

[0088] Values from multiple ROIs can be provided, and the intensities between different ROIs can vary significantly, especially the maximum intensity. The minimum effective bolus can be determined as the bolus providing the maximum intensity, which is a predefined coefficient multiplied by the standard deviation of the background noise level. In one embodiment, this must apply to all ROIs. However, in some cases, for example, the selected ROI does not provide a viable signal, such as when there is no perfusion in that section. In such cases, one or more ROIs can be discarded in the evaluation of the minimum effective bolus.

[0089] The aforementioned predefined coefficient can be at least 5, more preferably at least 10, even more preferably at least 25, and most preferably at least 50.

[0090] Once the minimum effective bolus has been determined, such as the subject-specific minimum effective bolus, the actual bolus to be used in an ongoing continuous and repeated measurement procedure can be that minimum effective bolus. However, to ensure an available signal, it can be determined that the actual bolus to be used is a certain percentage of the minimum effective bolus. The actual bolus used can be less than the determined viable bolus, but in particular, the actual bolus used can be greater than the minimum effective bolus, such as at least 125% of the minimum effective bolus, more preferably at least 150%, even more preferably at least 200%, and most preferably at least 300%. However, it is important to note that the actual bolus can vary over time and does not have to be set to a constant percentage value of the minimum effective bolus. Instead, the actual bolus can vary over time. For example, this is the case when an initial large actual bolus is injected and then a smaller actual bolus is injected. In this way, an initial large actual bolus that can be between 125% and 375% of the minimum effective bolus, more preferably between 150% and 350% of the minimum effective bolus, even more preferably between 175% and 325% of the minimum effective bolus, and most preferably between 200% and 300% of the minimum effective bolus can be used to saturate the intensity signal. Thereafter, after the initial large actual bolus, smaller actual boluses can be repeatedly injected at a constant percentage value of the minimum effective bolus (such as approximately 100% of the minimum effective bolus).

[0091] When determining the subject-specific minimum effective bolus, the boluses are injected at intervals of time between each bolus, preferably a predefined time period, but possibly a time period that can be adjusted based on the measured fluorescence measurements. The time period can also be customized for a particular situation (such as the subject). At least initially, the time period between injections is typically about 20 - 60 seconds, and may even be 20 - 40 seconds or 20 - 30 seconds. In other cases, at least when using ICG, the time period between injections is typically about 5 - 600 seconds, and may even be 30 - 300 seconds or 90 - 120 seconds, as this is the normal duration from the slope increase until the intensity decreases again sufficiently.

[0092] The time period from the injection of the fluorescent agent until fluorescence emission can be detected varies depending on the situation and generally can depend on, for example, tissue perfusion characteristics and blood flow characteristics, but can also depend on other individual factors of the patient, such as anatomical structure, tissue composition, and interaction kinetics, or other possible factors, such as the fluorescent agent, etc. This time period can be estimated, but it is advantageous if a specific time period is known. Thus, the system disclosed in the present application can be further configured to determine a subject-specific transition period, which is defined as the time period from the injection of the bolus of the fluorescence imaging agent to the increase in the fluorescence slope in the fluorescence emission of the anatomical structure.

[0093] The system disclosed in the present application can be further configured to determine a subject-specific interruption interval, which is defined as the time period from when the fluorescence slope starts to rise until the fluorescence emission equals the background noise, or until the fluorescence emission drops below a multiple standard deviation of the background noise, such as 20, 10, or 5 times the SD, i.e., the subject-specific time period during which there is detectable fluorescence emission.

[0094] The system disclosed in the present application can be further configured to determine a subject-specific rise + fall interval, which is defined as the time period from the rise of the fluorescence slope, through the maximum intensity, until the fluorescence emission drops below 50% of the maximum intensity, or more preferably 25% of the maximum intensity, even more preferably below 10% of the maximum intensity, still more preferably below 5% of the maximum intensity, and most preferably below 1% of the maximum intensity.

[0095] The system disclosed in the present application can be further configured to determine a subject-specific injection interval, which is defined as the time period from the injection of the fluorophore, the rise of the fluorescence slope, through the maximum intensity, until the fluorescence emission drops below 50% of the maximum intensity, or more preferably below 25% of the maximum intensity, even more preferably below 10% of the maximum intensity, still more preferably below 5% of the maximum intensity, and most preferably below 1% of the maximum intensity. Once the fluorescence emission drops below a certain intensity, a new bolus agent can be detected to quantify the fluorescence emission. That is, the subject-specific injection interval can be regarded as the time required to wait between subsequent micro-dose fluorophore injections. However, since it takes a certain amount of time for the subsequent bolus agent to reach the anatomical structure after injection, the subject-specific rise / fall interval defined above can also be regarded as the time required to wait between subsequent micro-dose fluorophore injections.

[0096] The properties of existing fluorophores (such as ICG) are well known, and the waiting time between subsequent injections can also be predefined. The rise / fall interval defined above is typically about 20 - 60 seconds, and can even be 20 - 40 seconds or 20 - 30 seconds. In another embodiment, the rise + fall interval defined above is typically about 5 - 600 seconds, and can even be 30 - 300 seconds or 90 - 120 seconds.

[0097] Instead of waiting for the fluorophore to wash out of the blood, the perfusion parameters can be determined after injecting the fluorophore of a new bolus before the previous bolus is removed / eluted. In particular, this is possible if the subsequent bolus is greater than the previous bolus, thereby also ensuring that an increased amount of fluorophore is administered. Accordingly, the system disclosed in the present application can be configured to automatically: 1) control an injection pump to inject boluses of a series of fluorescence imaging agents in an increasing or decreasing amount (e.g., an incremental or decremental amount), with a predefined time period between each bolus; and 2) determine at least one perfusion parameter of the anatomical structure after injecting each bolus. The incremental amount can start, for example, at 100% and increase linearly by 10%, such as 110%, 120%, 130%, 140%, etc. Or increase by 25%, i.e., 100%, 125%, 150%, 175%, etc. Or increase by 50%, i.e., 100%, 150%, 200%, 250%, etc. Or increase by 100%, i.e., 100%, 200%, 300%, 400%, etc. Or increase exponentially, such as 100%, 200%, 400%, 800%, etc.

[0098] The decremental amount can start, for example, at 200% and decrease linearly by 10%, such as 190%, 180%, 170%, 160%, etc. Or decrease by 25%, i.e., 200%, 175%, 150%, 125%, etc. Or decrease by 50%, i.e., 250%, 200%, 150%, 100%, etc. Or decrease by 100%, i.e., 400%, 300%, 200%, 100%, etc. Or decrease exponentially, such as 800%, 400%, 200%, 100%, etc.

[0099] Automated system

[0100] The system disclosed in the present application can be configured to determine the at least one perfusion parameter in one or more regions of interest located in the anatomical structure and optionally in adjacent anatomical structures. The system can be configured such that these regions of interest can be selected by a user of the system.

[0101] The system disclosed in the present application can be further configured to send the at least one perfusion parameter for presentation on a display. That is, so that medical personnel can track the progress of the perfusion assessment during a medical procedure. The display can be a white light picture with the parameters superimposed.

[0102] The system disclosed in the present application can further include at least one processor and a memory storing instructions thereon, the instructions when executed by one or more processors cause the system to perform what is disclosed herein.

[0103] An injection pump (also referred to as a drug pump) can be part of the automated perfusion assessment system disclosed in the present application. The injection pump can be configured to deliver a time-controlled, periodic infusion of a fluorophore to a target, such as a subject. Control of the injection pump can be provided by a programmable and / or controllable control unit. Thus, the control unit can be configured to automatically operate the injection pump to periodically infuse the fluorophore in boluses containing a controllable and / or predefined amount of the fluorophore according to the bolus doses disclosed herein and with a controllable and / or predefined duration between infusions. That is, the system can be configured only to control the injection pump, e.g., by a control unit configured to control the injection pump. Commercially available controllable injection pumps are available, e.g., the KDS single syringe pump (series 100) from Sigma-Aldrich, or the Legato 212 dual syringe pump from World Precision Instruments, or the Fusion controllable syringe pump from Chemyx.

[0104] The automated system disclosed in the present application can be external to an existing fluorescence imaging system, i.e., configured only to control the injection pump and receive time series fluorescence images from the existing system for analysis, e.g., an external system such as an endoscope and / or laparoscope device, e.g., the Novadaq Pinpoint endoscope fluorescence imaging system or the Novadaq Spy-Phi portable hand-held imaging system, where the imaging unit and optionally the light source are both included in the system. Existing laparoscope systems from Olympus, Stryker, Karl Storz or surgical robots from Intuitive can also be selected.

[0105] However, the system disclosed in the present application can also be a more complete fluorescence imaging system, e.g., an endoscope and / or laparoscope system, which can include one or more light sources for fluorescence excitation and their control. That is, in a further embodiment, the system further includes at least one light source configured to provide excitation light to induce fluorescence emission of the first and / or second fluorophore in the anatomical structure. For example, a near-infrared light source (e.g., for ICG) can be directly connected to the camera. Similarly for the imaging unit, i.e., the system can include an imaging unit configured to record at least one time series of fluorescence emission from the anatomical structure. For example, a digital video camera can record the emission of the fluorophore in real time, which means that perfusion can be evaluated and recorded in real time. The imaging unit can be further configured for white light imaging such that a normal image of the anatomical structure can be received and / or viewed, i.e., while recording the fluorescence signal with a separate camera. This can be provided by an additional camera in the imaging unit.

[0106] Accordingly, one embodiment of the present disclosure relates to a system for automatically assessing perfusion of an anatomical structure during a medical procedure on a subject, the system comprising:

[0107] - A controllable injection pump for containing at least one fluorescent imaging agent,

[0108] - At least one light source configured to provide excitation light to induce fluorescence emission of the fluorescent agent in the anatomical structure,

[0109] - An imaging unit configured to record at least one video sequence of the fluorescence emission from the anatomical structure,

[0110] wherein the system is configured to automatically control the injection pump, the light source, and the imaging unit for

[0111] - Injecting a predefined amount of the fluorescent imaging agent into the subject's bloodstream,

[0112] - After injecting the fluorescent imaging agent, inducing and analyzing the fluorescence emission from the anatomical structure,

[0113] - Determining at least one perfusion parameter of the anatomical structure based on the analysis.

[0114] Intraoperative fluorescence imaging

[0115] Using near-infrared light from a surgical microscope and acquiring a video of the fluorescence excited by a fluorescent angiography agent intravenously administered as a tracer in the near-infrared region enables perfusion (e.g., blood flow) to be imaged and evaluated in real time during surgery. Thus, the perfusion status during surgery can be confirmed in real time.

[0116] The systems and methods disclosed in this application can provide enhanced tissue characterization information, including the location of superficial and deeper blood vessels, especially when using different fluorescent agents, because careful selection of different fluorescent agents provides the option of obtaining perfusion information from different depths of the tissue.

[0117] During medical procedures such as diagnostic, screening, examination, and / or surgical procedures involving fluorescence imaging, a solvent containing a fluorescent contrast agent (e.g., ICG) is injected intravenously, and the molecule is excited by an infrared light source (e.g., a laser with a wavelength in the infrared wavelength range, e.g., about 780 nm). Fluorescence with a wavelength of about 830 nm is then emitted from the excited contrast agent molecules and can be recorded with an imaging device (e.g., in the form of a camera). A filter can be provided to block the excitation light, as the excitation intensity is typically much greater than the fluorescence intensity. The excitation intensity can be about 1 W per emission angle, while the fluorescence power pr. pixel can be about 0.15 pW. Despite the difference in several orders of magnitude, a good signal-to-noise ratio (SNR) can be achieved. The recorded fluorescence provides an image of the perfusion in the imaged tissue, and since the penetration depth of ICG is 5 - 10 mm, deeper blood vessels can be seen. Since the ICG molecules bind to proteins in the blood, the video image contains information about the perfusion level - but it is difficult for the surgeon to quantify this information during the surgery if only the acquired video image is seen.

[0118] In the systems and methods of the present disclosure, the fluorescent contrast agent is selected from: indocyanine green (ICG) and fluorescein isothiocyanate, rhodamine, phycoerythrin, phycocyanin, allophycocyanin, o-phthalaldehyde, fluorescamine, rose Bengal, trypan blue, fluorescent gold, green fluorescent protein, flavin, methylene blue, porphysomes, cyanine dyes, IRDye800CW, CLR 1502 conjugated to a targeting ligand, OTL38 conjugated to a targeting ligand, or a combination thereof.

[0119] Indocyanine green (ICG) is a cyanine dye used in medical diagnosis and is currently the most common dye used for perfusion assessment. It has a peak spectral absorption at about 800 nm. These infrared frequencies penetrate the retinal layers, enabling ICG angiography to image deeper circulatory patterns than fluorescein angiography. ICG binds tightly to plasma proteins and is confined to the vascular system. It is administered intravenously and is eliminated from the body through the liver into the bile according to the performance of the liver, with a half-life of about 3 - 4 minutes. ICG sodium salt is usually provided in powder form and can be dissolved in various solvents; typically, 5% (<5%, depending on the batch) of sodium iodide is added to ensure better solubility. The sterile lyophilized product of the ICG aqueous solution has been approved as a diagnostic agent for intravenous use in many European countries and the United States under the names ICG-Pulsion, IC-Green, and VERDYE.

[0120] The absorption and fluorescence spectra of ICG are in the near-infrared region. Typically, a laser with a wavelength of about 780 nm is used for excitation. At this wavelength, the fluorescence of ICG can be detected by filtering the scattered light from the excitation beam.

[0121] The toxicity of ICG is classified as low, but administration is not without risks, such as during pregnancy. It is known that ICG decomposes into toxic waste under the influence of UV light, producing many substances that are still unknown. That is, as demonstrated herein, minimizing the dose of ICG used during fluorescence imaging is in the interest of the patient.

[0122] Fluorescein is another dye that is widely used as a fluorescent tracer for many applications. Fluorescein has a maximum absorption at 494 nm and a maximum emission (in water) of 512 nm. Therefore, it is suitable for use in combination with ICG because the absorption and emission wavelengths of the two dyes are separated by several hundred nanometers.

[0123] Automatic perfusion assessment method

[0124] As previously mentioned, the present disclosure also relates to a method for automatically assessing the perfusion of a subject's anatomical structure, the method comprising administering a bolus agent intravenously, the bolus agent having approximately 1 / 10 of the normal dose for perfusion assessment. For indocyanine green (ICG), the normal bolus agent is 0.1 - 0.3 mg / kg body weight. According to the present disclosure, a bolus agent of less than 0.01 mg / kg body weight of the first fluorescent imaging agent can be used. For other fluorescent imaging agents described herein, the bolus agent is similarly reduced according to the present disclosure. As described above, the agent can be injected by a controllable injection pump, for example, in a series of bolus injections, with a predefined time interval between subsequent bolus injections. After each bolus injection, the fluorescence emission from the anatomical structure can be measured.

[0125] The minimum bolus agent can be determined after administering a series of increasing bolus agents, the minimum bolus agent providing a quantifiable fluorescence emission bolus agent representative of the perfusion of the anatomical structure. The bolus agent can include an increasing or decreasing amount of the agent, for example, the amount can increase or decrease from one bolus agent to the subsequent bolus agent in 10% increments.

[0126] The interval between bolus injections can be 5 to 600 seconds, such as 5 to 300 seconds, such as 10 to 180 seconds, such as 10 to 140 seconds, such as 10 to 90 seconds, such as 15 to 80 seconds, such as 20 to 70 seconds, such as 30 to 60 seconds. In another embodiment, the interval between bolus injections can be 5 to 600 seconds, such as 10 to 600 seconds, such as 15 to 600 seconds, such as 15 to 300 seconds, such as 30 to 240 seconds, such as 45 to 240 seconds, such as 90 to 240 seconds, such as 90 to 120 seconds. The interval between bolus injections is preferably long enough to allow measurement of the perfusion slope in the anatomical structure for each bolus injection, preferably, wherein the perfusion slope includes a slope start point and an elution slope.

[0127] For ICG, the amount of the fluorescent imaging agent is preferably from 0.0001 to 0.01 mg / kg body weight per bolus, such as from 0.001 to 0.01 mg / kg body weight per bolus. The initial amount of the fluorescent imaging agent is advantageously at least 0.001 mg / kg body weight. The subsequent boluses increase by at least 0.001 mg / kg body weight from one bolus to the subsequent boluses. For other types of fluorescent imaging agents, the dose is preferably selected based on its fluorescence relative to ICG. Thus, it is preferred to administer a fluorescent imaging agent with a higher emission rate at a correspondingly lower dose. The dose can be, for example, substantially inversely linear with the quantum yield of the fluorescent imaging agent. The dose can further be based on the absorption and emission spectra relative to ICG.

[0128] The bolus is preferably a liquid volume of 0.5 μL to 10 mL, such as 0.5 - 5 mL. In a preferred embodiment of the present disclosure, a volume of an isotonic solution (such as saline) is immediately injected after injecting the fluorescent imaging agent of the bolus, such as where the volume of the isotonic solution is 1 - 20 mL, such as 2.5 - 15 mL, such as 5 - 10 mL.

[0129] In a further embodiment of the present disclosure, a second fluorescent imaging agent is administered, and the emission maximum of the second fluorescent imaging agent differs from the emission maximum of the first fluorescent imaging agent by at least 50 nm or at least 100 nm. The first and second fluorescent imaging agents are preferably administered alternately. Advantageously, the interval between the administrations of different fluorescent imaging agents is half of the interval between subsequent administrations of the same fluorescent imaging agent.

[0130] In a further embodiment of the method disclosed in the present application, a series of fluorescent images of the anatomical structure are formed for perfusion assessment. Fluorescence can be automatically detected by irradiating the anatomical structure with a light source capable of exciting the fluorescent imaging agent, and the emission can be quantified by a series of fluorescent images of the anatomical structure.

[0131] The interval between boluses is determined by a computer configured to detect the perfusion slope caused by each bolus. Additionally, the amount of the fluorescent imaging agent in the bolus can be controlled by a computer configured to determine the minimum bolus corresponding to the minimum fluorescent emission representative of the perfusion of the anatomical structure. The computer can be part of the system disclosed in the present application.

[0132] In a further embodiment, perfusion assessment includes determining the location of perfusion complications in the anatomical structure. Thus, perfusion assessment can be used in combination with a diagnostic or surgical procedure, for example, the procedure includes diagnostic laparoscopy, exploratory laparoscopy, surgical laparoscopy using conventional laparoscopy, robotic surgery, and open surgery. The procedure can optionally include anastomosis, such as intestinal anastomosis; wounds; plastic surgery; cardiac surgery or cancer.

[0133] A further embodiment of the present disclosure relates to a fluorescent imaging agent for use in the methods disclosed herein. Another further embodiment relates to the use of a fluorescent imaging agent in the preparation of a medicament for use in the method for automatic perfusion assessment disclosed herein.

[0134] In a further embodiment of the present disclosure, the fluorescent imaging agent can be injected repeatedly. In some cases, a longer time period may be required, for example at least 2 minutes, preferably at least 3 minutes, even more preferably at least 4 minutes, even more preferably at least 5 minutes, almost most preferably at least 8 minutes, most preferably at least 10 minutes, during which no fluorescent imaging agent is injected in order to allow the fluorescent imaging agent to be washed out, thereby reducing the background level. Once the background level has been reduced to an acceptable level, for example below a certain percentage of the maximum fluorescence intensity, or until fluorescence is essentially undetectable, injection of the fluorescent imaging agent can be continued.

[0135] The system disclosed in the present application can be configured to perform the method for automatic perfusion assessment of an anatomical structure disclosed above. This can be provided by a system having at least one processor and a memory storing instructions thereon, the instructions when executed by one or more processors cause the system to perform the method for automatic perfusion assessment of an anatomical structure disclosed in the present application.

[0136] Perfusion parameters

[0137] Various parameters can be determined based on image analysis of fluorescence emission. Intensity values relative to time are typically extracted from the image analysis, and these values can be used to generate a number of time-course curves, and the shape of the time-course curves can be analyzed. Based on this analysis, that is, based on the results of image analysis of time-series fluorescence images (also referred to as video-sequence fluorescence images), relative and / or quantitative data on perfusion, blood volume, and / or blood flow can be determined. In particular, the perfusion slope of the flow of a fluorescent contrast agent through at least one region of interest can be determined. The perfusion slope is a key parameter because it is a direct indication of perfusion in the imaged tissue.

[0138] Perfusion parameters can be determined from fluorescence intensity values extracted from one or more regions of interest (usually including tissue). The configuration of the regions of interest, such as the size of the region, the number of regions, the position in the image, etc., can be provided automatically, semi-automatically, or manually by a user (e.g., a doctor / surgeon). Through at least some manual intervention, the user can select additional regions of interest or remove existing regions of interest. Preferably, one or more regions are also moved around in the image such that the regions of interest are located in relevant regions of the image, preferably prior to the capture of the video sequence.

[0139] The perfusion slope can be determined from the fluorescence intensity values integrated over the entire region of interest including the tissue. Initially, before the injection of the contrast agent, the curve will be a substantially flat line. After the injection of the contrast agent, once the bolus of contrast agent molecules is excited and reaches the region of interest, the region of interest will start to fluoresce - resulting in a line that increases substantially linearly. When the bolus of contrast agent molecules levels off, the fluorescence intensity in the region of interest will also level off and start to wash out as the amount of contrast agent molecules decreases (substantially linearly) to zero.

[0140] However, this is an idealized scenario and the curve can vary over time and between patients, so it is important to define the perfusion parameters robustly such that they can be determined automatically on the fly and are repeatable and comparable.

[0141] The perfusion slope can be defined by the slope of the intensity values extracted from the start point to the end point of the slope. The perfusion slope can be determined only as a linear fit to the curve. The challenge lies in determining the start point (slope start point) and the end point (slope end point) of the fit, especially in real-time situations. The slope start point is the most important of the two and can be defined as the time point when the slope exceeds a predefined first threshold. The first threshold can be determined, for example, by three parameters: a predefined coefficient k, and the mean and standard deviation (std) of the intensity values before the slope start point or before the supply of the fluorescent contrast agent. The slope start point can then be defined as the time point when the slope exceeds the mean + k*std. The slope end point can be defined accordingly as the time point after the slope start point when the slope decreases by more than a predefined second threshold. The constant k can be determined according to the settings, but typically k is in the range of 3 - 10.

[0142] However, advantageously, the perfusion slope can be determined from a histogram of the parameter space of all the slopes binned after the slope start point, and where the perfusion slope is determined as the most frequent value of the histogram. That is, after the slope start point, the slope values are calculated for all subsequent intensity points based on the slope start point. The slope end point can then be derived therefrom. Greater weight can be assigned to the slope values calculated immediately after the slope start point in the histogram than to later slope values, since it is certain that the perfusion slope has started after the slope start point. For example, weights of 100, 99, 98... etc. can be assigned to the first 100 calculated slope values respectively in the histogram. If a higher constant k is chosen, even more weight can be assigned to the initial values of the perfusion slope. The histogram-centered method is very precise and can advantageously be used in real-time or near-real-time situations.

[0143] Another parameter that can be determined is the washout slope, which represents the regressive flow of the contrast agent, for example, through at least one of the regions of interest. However, since the flow of the contrast agent increases, the perfusion slope is typically positive, while the washout slope is opposite to the perfusion slope (in terms of sign), i.e., typically negative. The washout slope can add information about the perfusion in the tissue. However, the washout slope can also be related to an indication of the function of an organ (such as the liver). Similar to the perfusion slope, the washout slope can be defined by the slope of the intensity values from the washout start point to the washout end point. The washout start point appears after the slope end point. The washout slope can be determined by a histogram of the parameter space that bins all the slopes after the washout start point, and where the washout slope is determined as the most frequent value of the histogram. As described above for the perfusion slope, greater weights can be assigned to certain calculated washout slope values in the histogram compared to other values, especially the initial values of the washout slope after the washout start point.

[0144] The maximum intensity reached can be easily determined, for example, for each ROI. However, a more relevant parameter can be the maximum slope intensity, which is the intensity at which the intensity values start to level off. The maximum slope intensity can be defined as the intensity value at the slope end point. A more precise definition can be the intensity value at the time point when the distance from a straight line (which has the gradient perfusion slope and intersects the curve point determined by the slope start point) exceeds a predefined limit value (such as based on, for example, the standard deviation of the perfusion slope). For example, the maximum slope intensity can be at a position where the intensity level differs from the perfusion slope by a predefined coefficient multiplied by the standard deviation of the perfusion slope.

[0145] The slope rise time can also be relevant and can be defined as the difference between the time points of the maximum slope intensity and the slope start point, i.e., the time taken for the contrast agent to flow through or accumulate in the tissue, which can be an indication of the blood flow velocity.

[0146] The relative perfusion slope can then be defined as the reciprocal of the slope rise time. The subject-specific relative perfusion slope can then be defined as the relative perfusion slope multiplied by the maximum intensity of the region of interest where the perfusion is at a local (or global) extreme. That is, the perfusion parameter that is normalized to become a patient-specific perfusion slope parameter.

[0147] Tracking

[0148] In a further embodiment, tracking of the movement of an anatomical structure (such as the gastrointestinal tract) in time-series images (such as video images) is provided. Thus, the systems and methods disclosed in the present application can employ tracking, as exemplified below, so that perfusion parameters can be extracted from the same anatomical structure and the same part of the anatomical structure in repeated / continuous measurements. The movement of the anatomical structure or at least a part thereof can be used such that at least one region of interest corresponds to the same part of the anatomical structure in the video image.

[0149] Especially in open surgery, the camera can move around during the operation. Therefore, during the operation and during continuous perfusion measurement, the selected ROI may completely disappear from the image. The tracking disclosed herein also relates to identifying when the relevant region and / or anatomical structure is within the image - and when it is not within the image, so that perfusion parameters measured from completely different regions are not erroneously compared.

[0150] The purpose of tracking is mainly to ensure that the data (e.g., pixel intensity values) is sampled from the same tissue region. Therefore, if the anatomical structure moves in the image, the tracking should ensure that any region of interest as defined herein will move accordingly to ensure that the sampled data for the region of interest is understandable. In this regard, it does not matter whether the anatomical structure physically moves, e.g., due to the subject's breathing and / or peristalsis, or the imaging device acquiring the image moves relative to the anatomical structure. What matters is whether the object being imaged moves within the acquired image.

[0151] Accordingly, another aspect of the present disclosure more generally relates to a computer - implemented method for processing the motion / dynamics of at least a portion of an anatomical structure (e.g., during a medical procedure) from video images representative of at least an external portion of the anatomical structure, the method comprising the steps of:

[0152] - selecting one or more regions of interest in at least one of the video images, at least a first of the regions of interest corresponding to a part / sub - part of the anatomical structure,

[0153] - tracking the motion of the anatomical structure in the video image, and

[0154] - correlating the motion of the anatomical structure such that at least the first region of interest corresponds to the same part of the anatomical structure in the video image.

[0155] Tracking of an object in an image sequence (e.g., a video sequence) can be provided in different ways. Roughly speaking, there are at least two different methods: free - image tracking (FIT) based only on the input video source and object - based tracking (OBT), where a predefined and / or recognizable object is associated with the object being tracked in the image.

[0156] Free image tracking can be provided, for example, by a classifier: based on the input image, the classifier algorithm calculates a classifier of the most recognizable features in the area surrounding a given ROI (for more ROIs, a sensitive area will be assigned to each ROI, within which the tracking applies to the given ROI). In one embodiment of the present disclosure, motion tracking of anatomical structures is provided by free image tracking, for example, in the form of classifier-based tracking, which includes the following steps: determining a classifier of a more recognizable feature in a video image (preferably in an area adjacent to or surrounding at least one area of interest).

[0157] Free image tracking can also rely on color-based tracking: prior to a medical procedure such as surgery, at least one ROI of an object (e.g., an anatomical structure, e.g., the intestine) has been marked with a color and / or pattern (preferably, a predefined color or pattern). The marking can be provided, for example, by a surgeon. If the actual ROI has been marked, the color-based algorithm can obtain the form of the marking and use this form as a specific area of interest. The color-based algorithm can be configured to first perform color filtering and then perform object confirmation. Based on the nature of the marking (mainly color), target RGB or HSV indices can be provided for filtering. Then, filtering can be provided, for example, in the form of an HSV threshold to obtain a Boolean map of the input image pixels, and this Boolean map will only contain pixels covering the marking. Then, object confirmation can be provided, for example, by noise filtering, for example, by opening or closing based on erosion / dilation, in order to remove noise from the Boolean map. Using these noise filters, an improved Boolean map with "filled" ROIs can be obtained. That is, the resulting Boolean map is filled with zeros except for patches filled with 1 (or vice versa), and each patch will correspond to an ROI.

[0158] Another example of free image tracking is based on cross - correlation: after selecting an ROI image (usually a "normal" white - light image), the area within each ROI is stored as the initial reference for each ROI. These initial ROI references are then subsequently used as templates in, for example, a cross - correlation function for continuous and / or real - time applications, as the tracking function for each ROI. The cross - correlation function can be in the form of pattern recognition and can be regarded as a measure of similarity, as a function of the displacement of two images relative to each other, i.e., it is well - suited to be used as a tracking function. For example, at least initially, the actual tracking function can be limited to the area adjacent to each ROI, since in most cases, the actual movement will be periodic. During a medical procedure, additional ROI images can be acquired and stored. If these additional ROI images are acquired as the basis for an average, the initial template can be improved (possibly continuously), resulting in a new (and possibly final) ROI template for use in tracking. Such an improved template that includes information from several ROI images thus includes a temporal aspect. This can make the tracking better and / or more efficient. For example, if tracking intestinal movement, the intestine rolls back and forth during the procedure. When only using the initial template ROI for tracking, it may be more difficult to track the ROI at each position of the rolling motion, but if using an average template that takes the average of multiple templates from the rolling motion, it is much easier to track the ROI at each position of the rolling motion.

[0159] In object - based tracking, one or more objects are physically attached to the target that must be tracked, such as the intestine. Since the (one or more) objects are usually predefined according to, for example, size, shape, and color, a classifier can be trained before tracking, i.e., the tracking system used can be configured to automatically recognize (and thereby track) the predefined object. In one embodiment of the present disclosure, anatomical structure motion tracking is provided by object - based tracking, for example, by tracking the movement of one or more predefined objects attached to an anatomical structure.

[0160] As an example of object-based tracking, two (or more) spheres (or another geometrically well-defined object) can be attached to the "top" of an anatomical structure and one (or more) spheres attached to the lower / bottom part of the anatomical structure (as seen from the imaging device). If the objects attached to the top are different from those attached to the bottom, it is easy to distinguish the top from the bottom. If the spheres emit trackers, they are even more easily recognizable and thus easy to track. They can, for example, contain a fluorescent agent such that the spheres are visible when excited. They can then be identified in the image by, for example, Hough circle identification (or another feature extraction). They can also be colored and identified by the above color identification method. Since the "top" / "bottom" objects are predefined and thus known in advance, it is easy to train a classifier for these two types of objects. To train a classifier for the objects, a large picture database of the said objects can be used to train the classifier. By using the classifier, the positions of the "top" and "bottom" objects in the image can be determined very precisely.

[0161] Since the objects are fixed to the target, such as the tissue of the intestine, ROIs can be defined based on these objects (such as "top" and "bottom"). For example, in the case of using four objects, the ROI corners can simply correspond to the positions of the four tracked objects. In the case of two objects, an ROI can be defined between the two object positions: for example, a parallelogram, extending from the middle to half height - this determines the angle.

[0162] It should also be noted that tracking is not limited to determining the two-dimensional position / coordinates of the region of interest. Instead, tracking can be implemented in such a way as to determine the position / coordinates of the region of interest in all three dimensions with respect to Euclidean space. For three-dimensional reconstruction of objects, a variety of imaging methods are known. For example, these methods include methods based on oblique illumination (where the object is illuminated from the side), microscopy techniques (such as confocal microscopy, light sheet fluorescence microscopy, 3D deconvolution microscopy), and other methods where the properties of known objects are used to obtain depth information. Other methods for obtaining depth information are known to those skilled in the art and can be used in combination with the systems disclosed in the present application to accurately track the region of interest in three dimensions. The depth information obtained is preferably used by the system to evaluate the measured perfusion metric, for example, by normalizing the measured fluorescence intensity based on the distance to the region of interest.

[0163] Perfusion assessment

[0164] A lot of valuable information can be obtained from the above perfusion parameters. However, in order to define the perfusion parameters, some kind of reference may be needed.

[0165] In one embodiment, video sequences obtained from different parts of an anatomical structure can be used to calculate perfusion parameters related to each part, and these perfusion parameters can be compared such that perfusion in different parts of the anatomical structure can be compared. That is, perfusion parameters obtained from one video sequence can be used as a reference such that a quantitative assessment of perfusion can be provided between video sequences related to different parts of the anatomical structure.

[0166] In another embodiment, different regions of interest can be selected from the same video sequence such that perfusion parameters related to one region of interest are used as a reference for other regions of interest, thereby providing a quantitative assessment of perfusion between different regions of interest in the same video sequence. These different regions of interest can be selected such that they represent different parts of an anatomical structure or different but adjacent anatomical structures. For example, if the anatomical structure is the gastrointestinal tract, different parts of the gastrointestinal tract can be the colon and the small intestine. For example, surgery can be performed on the colon, but by comparing with the small intestine, which is typically located near the colon in the body and can thus be imaged during video acquisition, a reference that is not affected by the surgery can be provided. Another example is a prospective flap compared to healthy skin with good perfusion in plastic surgery.

[0167] That is, at least a first perfusion parameter is determined, such as the flow of a fluorescent contrast agent through at least the first said region of interest, the first perfusion parameter being selected from: perfusion slope, washout slope, maximum slope intensity, relative perfusion slope, and subject-specific relative perfusion slope, and at least a second perfusion parameter is determined, such as the flow of a fluorescent contrast agent through at least a second region of interest, the second perfusion parameter being selected from: perfusion slope, washout slope, maximum slope intensity, relative perfusion slope, and subject-specific relative perfusion, where the first and second regions of interest represent different parts of an anatomical structure or different anatomical structures. Then, perfusion in one of the different parts of the anatomical structure can be evaluated by comparison with perfusion in at least another of the different parts.

[0168] Accordingly, a further embodiment includes the steps of:

[0169] - performing image analysis on at least the following two video sequences, each video sequence being obtained after supplying a fluorescent contrast agent to a subject:

[0170] ○ a first video image representing at least a first part of an anatomical structure or at least a first anatomical structure, and

[0171] ○ a second video image representing at least a second and different part of an anatomical structure or at least a second and different anatomical structure,

[0172] - calculating intensity values in one or more regions of interest based on the image analysis of the first video image and the second video image, and

[0173] -Determine the perfusion slope of the fluorescent contrast agent flowing through at least a first region of interest selected in the first video sequence and through at least a second region of interest selected in the second video sequence.

[0174] Another embodiment more particularly relates to an anastomosis procedure, where perfusion assessment can be an important indicator of where resection is to be provided and whether the final anastomosis has sufficient perfusion. Thus, a further embodiment also includes the steps of:

[0175] -Perform image analysis on two or more of the following video sequences, each video sequence being acquired after supplying a fluorescent contrast agent to a subject:

[0176] a) Video images acquired before intestinal resection (e.g., bowel resection),

[0177] b) Video images acquired after resection but before anastomosis, and

[0178] c) Video images acquired after anastomosis.

[0179] -Based on the image analysis, calculate the intensity values in one or more regions of interest, wherein at least the first said region of interest is the same region in the two or more video sequences, and

[0180] -Based on the two or more video sequences, determine the perfusion slope of the fluorescent contrast agent flowing through at least the first region of interest.

[0181] Based on the two or more video sequences, one or more of the following parameters can be determined based on the two or more video sequences: washout slope, maximum slope intensity, relative perfusion slope, and subject-specific relative perfusion slope.

[0182] Parameters having two (or more) video sequences obtained at different times during a medical procedure enable the use of parameters extracted from one video sequence as reference parameters. Thus, quantitative data of perfusion in at least one of the regions of interest based on slope parameters can be determined according to the at least two video sequences. As a result, quantitative and qualitative evaluation parameters can be provided to a surgeon during and after a medical procedure such as a gastric surgery, for example, to assist in evaluating whether an intestinal (e.g., bowel) resection looks promising. During and after the surgery, the results can be evaluated almost immediately, for example, to assess whether an anastomosis has sufficient perfusion. For example, this can be done by comparing perfusion parameters obtained continuously before, during, and / or after the surgery or during the medical procedure in order to quantify perfusion changes. Tracking of movement may be key to accurately quantifying perfusion changes as it is a way to ensure that the evaluation of perfusion is being carried out continuously in the same region of interest before, during, and / or after the surgery or during the medical procedure.

[0183] Thresholds specific to perfusion parameters can be provided. Also, an uncertainty can be associated with a given threshold. Threshold comparison can, for example, indicate whether an operation is going well or whether the perfusion according to the parameter in question has dropped below a critical level. For several perfusion parameters, a “weighted average answer” can also be provided.

[0184] In one embodiment of the present disclosure, a perfusion slope (and / or other perfusion parameters as described) is calculated based on a video sequence obtained before resection and a video sequence obtained after resection but before anastomosis. The relationship between the two perfusion slopes is a measure of the perfusion difference before and after resection. If the perfusion drops below a predefined threshold after resection, a warning can be given. If perfusion slopes are calculated before and after resection for two, three, or more regions of interest, more information can be extracted - these regions of interest are the same tissue areas imaged before and after resection.

[0185] Oscillatory kinetics

[0186] The inventors further recognized that the measurement and analysis of repeatable bolus injections can be extended from the interpretation and quantification of a single inflow and / or a single outflow phase to the analysis of oscillatory fluorescence kinetics. These oscillatory fluorescence kinetics can reveal physical perfusion characteristics that have hitherto been inaccessible without invasive measures.

[0187] The systems and methods disclosed herein can be configured to repeatedly inject small boluses, such as minimal boluses, at regular intervals. Depending on, for example, the injection time interval, these boluses can result in a periodic change that, when measured, takes the form of an approximate sine curve. In such a curve, it is expected that the measured intensity signal increases as the fluorescent imaging agent flows in from a given bolus and then decreases during the washout phase of the bolus until it increases again under a subsequent bolus, and so on, resulting in a periodic (sine) pattern.

[0188] Preferably, the system is configured such that it can identify parameters of the oscillating intensity curve, such as frequency and / or amplitude. Then, the trained system can in turn predict the direction and regularity of upcoming signal dynamics. The system preferably uses the measured values to identify the oscillating pattern such that the system can thereafter detect the difference between the measured values and the expected values. The measured values can be further continuously used to improve the pattern recognition, i.e., the expected values. Alternatively or additionally, injection parameters such as bolus frequency, dose, and flow rate can be used to determine the expected values, i.e., the oscillating pattern.

[0189] By predicting the expected values with the system, it can detect and prompt the onset of an ischemic condition at an early time point - ideally instantaneously. The detection of the ischemic condition can be a function of the (one or more) expected values and the (one or more) detected values, such as a threshold.

[0190] The difference from the expected sine curve pattern can be caused by, for example, the onset of an ischemic condition in at least a portion of the anatomical structure visible in the video image, or regional variations in perfusion to a given area. Illustrative figures are given in Figure 12A that demonstrate such kinetic changes due to an ischemic episode in a human subject, and a zoomed-in view of a narrower range is given in Figure 12B As can be seen, the transition from a regular oscillating fluorescence signal to an ischemic flat line can be detected. However, it should be noted that focusing on regional variations in perfusion of the anatomical structure can result in measurement patterns other than an ischemic flat line. One example is venous occlusion, where the outflow of blood from the anatomical area is blocked or reduced due to congestion or accumulation of the fluorescent agent in a given area, resulting in changes in the oscillating dynamics. As can be seen from Figure 13C although the cyclic oscillation stops, the result is not a flat line.

[0191] As described herein, such a system can observe and detect changes in the perfusion level of a given area in a video image within a few seconds. This can be detected in an area that has been observed for a long time (e.g., many minutes) in which the dynamics have been continuously visualized and thus the phase is well known. In Figure 12CAn illustrative diagram is shown that highlights the differences between the signals one would expect to observe for ischemic / healthy tissue regions. However, it can also be determined in anatomical regions that can only be visualized for a short time interval (e.g., 10 - 20 seconds), since the system is trained to expect and detect a certain phase of the described oscillatory dynamic signal in tissue, consisting of a regular rise and fall of the time-intensity signal. See Figure 12D , which shows how the anatomical region would look if the focus of the recorded image drifts in and out.

[0192] Preferably, the system includes tracking means and is capable of operating independently in the background, while the surgeon is only exposed to visible white light signals and is thus only interrupted / notified by warning signals. During, for example, the detection of the onset of an ischemic condition.

[0193] Another aspect of the present disclosure relates to continuous perfusion assessment related to repeated injection of a fluorescent agent and monitoring of the resulting oscillatory curves. In addition to detecting unforeseen perfusion changes, the system can also be used to evaluate the perfusion area of an artery. For example, a surgeon may consider incising an artery as part of a surgical procedure. Before incising the artery, the surgeon can temporarily restrict the perfusion through the artery, and the method disclosed in the present application can enable visualization of the perfusion area of the artery within a short time period (e.g., less than 1 minute). This can be valuable information for the surgeon during a continuous surgical procedure. In a similar manner, the system can be used to evaluate the drainage area of a vein or a group of veins, lymphatic vessels, lymph nodes, or other parts of the circulatory and / or lymphatic pathways. By temporarily restricting the blood flow through a blood vessel, the blood will accumulate in the anatomical region normally drained by that blood vessel or that group of blood vessels. This enables visualization of the anatomical region drained by that blood vessel within a relatively short time period (e.g., less than 2 minutes). This can provide important information to the surgeon in fields such as general surgery and plastic surgery (including wound and reconstructive surgery), for example, during a continuous surgical procedure.

[0194] Anatomical structure

[0195] The anatomical structure of the system and method disclosed in the present application can be the internal organs of a subject. Then, perfusion will typically be evaluated in the tissue outside the organ. Alternatively, the anatomical structure can be (a part of) the skin of the subject. Then, perfusion will typically be evaluated in the skin tissue.

[0196] Perfusion assessment of a wound is also highly relevant. Thus, the anatomical structure can include at least one wound, which will be the subject of the perfusion assessment.

[0197] The anatomical structure may be the gastrointestinal tract, preferably including the buccal cavity; pharynx; small intestine, including the duodenum, jejunum, and ileum; stomach, including the esophagus, cardia, and pylorus; large intestine, including the cecum, colon, rectum, and anal canal.

[0198] gastrointestinal tract

[0199] Complications related to the gastrointestinal tract are usually related to local hemodynamics. That is, changes in normal hemodynamic conditions can indicate an increased risk of complications. Therefore, when examining the gastrointestinal tract, such as for diagnosing complications or determining the location of complications, for example, during diagnostic laparoscopy, exploratory laparoscopy, or surgical laparoscopy or robotic surgery using conventional laparoscopy, as well as during open surgery, perfusion assessment of the gastrointestinal tract (especially on and near the surface of the gastrointestinal tract, such as the tissues of the gastrointestinal wall) can be an important diagnostic tool. Perfusion assessment is also important during a surgical procedure to form an anastomosis that can provide for establishing communication between two previously distant parts of the gastrointestinal tract. As an example, an intestinal anastomosis establishes communication between two previously distant parts of the intestine and generally restores the continuity of the intestine after removing the pathological condition affecting the intestine. Providing an intestinal anastomosis can be used, for example, for the following aspects: 1) restoring the continuity of the intestine (e.g., bowel) after resection of diseased intestine, and 2) bypassing non-resectable diseased intestine, such as bowel. Certain pediatric conditions may also require intestinal anastomosis [6].

[0200] The diseased bowel can be resected in the following circumstances:

[0201] · Gangrene of the bowel, which is caused by impaired blood vessels due to mesenteric vascular disease, long-term intestinal obstruction, intussusception, or volvulus

[0202] · Malignant tumor

[0203] · Benign diseases (e.g., intestinal polyps, intussusception, ascariasis infection with intestinal obstruction)

[0204] · Infection (e.g., tuberculosis complicated by stricture or perforation)

[0205] · Traumatic perforation

[0206] · Large perforations (traumatic) that cannot be repaired by primary suture

[0207] · Radiation enteritis complicated by bleeding, stricture, or perforation

[0208] · Inflammatory bowel disease, ulcerative colitis, or Crohn's disease, which is refractory to drug therapy or accompanied by complications (e.g., bleeding, perforation, toxic megacolon, dysplasia / cancer)

[0209] · Chronic constipation, idiopathic slow transit constipation, or Hirschsprung's disease: If the disease is refractory to medical therapy, subtotal colectomy may be performed.

[0210] The diseased bowel that cannot be resected can be bypassed in the following circumstances:

[0211] · Locally advanced tumors causing luminal obstruction

[0212] · Metastatic disease causing intestinal obstruction

[0213] · Poor general condition or conditions where extensive resection is not possible

[0214] Pediatric conditions where intestinal anastomosis may be required include the following:

[0215] · Congenital anomalies (e.g., Meckel's diverticulum, intestinal atresia, malrotation with volvulus leading to gangrene, meconium ileus, duplication cysts, Hirschsprung's disease)

[0216] · Inflammatory conditions (e.g., necrotizing enterocolitis, enterocolitis, tuberculosis, intestinal perforation)

[0217] · Other conditions (e.g., intussusception, angiodysplasia, polyposis diseases, ascariasis)

[0218] · As part of other surgical procedures (e.g., Kasai portoenterostomy, choledochal cyst, urinary diversion, pancreatic tumors)

[0219] Unfortunately, postoperative complications related to gastrointestinal anastomosis often occur, which are usually due to insufficient perfusion (capillary blood supply) at the anastomosis (i.e., the connection of two parts of the intestine). Insufficient perfusion can lead to anastomotic leakage, which is a serious and frequent complication, for example, related to colorectal surgery, where more than 10% of surgeries result in complications. In colorectal cancer surgery, more than 30% of patients with anastomotic fistulas die due to postoperative complications, and about 25% of the remaining patients are affected by stomas for life. Risk factors associated with fistulas include anastomotic tension, tissue damage, especially reduced blood perfusion.

[0220] Thus, in one embodiment, the present disclosure relates to performing image analysis on one or more video sequences representing at least a portion of the gastrointestinal tract obtained, for example, before, during, and / or after surgery, particularly surgery involving the gastrointestinal tract. This can be particularly applicable to gastrointestinal surgery - thus, the video sequence can include the exterior of at least a portion of the gastrointestinal tract, preferably such that perfusion in at least a portion of the gastrointestinal wall can be measured and evaluated.

[0221] The gastrointestinal tract is an organ system in humans and other animals that ingests food, digests food to extract and absorb energy and nutrients, and excretes the remaining waste as feces and urine. The gastrointestinal tract can be regarded as a pipeline for transferring food to the digestive organs. Therefore, the term gastrointestinal tract as used herein includes the buccal cavity; pharynx; small intestine, including the duodenum, jejunum, and ileum; stomach, including the esophagus, cardia, and pylorus; large intestine, including the cecum, colon, rectum, and anal canal. Examples

[0222] The intensity curves shown in the examples are the result of injecting a bolus with a normal amount of a fluorophore (in these cases, ICG). The amount of ICG in each bolus was chosen to make the fluorescence emission visible to the human eye. The examples are provided to illustrate the various perfusion parameters that can be calculated after fluorescence imaging. These same parameters can also be determined to a large extent after injecting a much smaller dose, i.e., the microdose method disclosed herein that employs potentially repeated and continuous measurements and associated perfusion assessments.

[0223] Figure 1A , 1C Figures 1E show examples of intensity curves obtained from tissue after providing an ICG bolus to a subject, e.g., from a region of interest in a video sequence. The same type of data can be obtained if another contrast agent is used. The intensity is essentially zero until a sharp rise in intensity indicates the passage of ICG molecules through the imaging tissue, where the ICG molecules are excited to fluoresce. After the intensity peak, the ICG molecules are gradually washed out. The intensity is expressed in arbitrary units. Figure 1B , 1D Figures 1F show the corresponding intensity curves in which the hemodynamic parameters perfusion slope, slope start, slope end, maximum intensity, washout slope, washout start, and washout slope end have been calculated and are shown in the figure.

[0224] Figures 2A - 2F show three examples that illustrate the method disclosed herein for determining the time point at which the perfusion slope starts (i.e., the slope start). Figure 2B , 2D and 2F are close-ups of Figure 2A , 2C and 2E, respectively, where the slope starts, i.e., the right-hand figure shows a close-up of the left-hand curve where the slope start is more detailed. It can be seen that the slope start is defined as the time point at which the slope exceeds the mean k*std, where k is a predefined constant and std is the standard deviation of the intensity values before the slope start. The slope start is indicated by a circle in Figure 2B .

[0225] Figures 3A - 3F show three examples that illustrate the method disclosed herein for determining the perfusion slope based on histogram data. The left-hand figure shows the intensity curve, whereFigure 3A corresponds to Figure 2A , Figure 3E corresponds to Figure 2E . The slope starting point is indicated by an arrow in Figure 3A and is indicated by a circle in Figure 3C and 3E . For all possible slopes of the intensity curve from the slope starting point to the end of the intensity curve, all calculated slopes have been collected and binned in the histogram shown on the right. The perfusion slope is defined as the most frequent value of the histogram, i.e., the highest histogram bin. Figure 3A , 3C and the calculated perfusion slopes for each intensity curve in 3E, i.e., Figure 3B , 3D and the highest histogram bars in 3F, are marked with a straight line in Figure 3A , 3C and 3E.

[0226] Figures 4A - 4F Three embodiments are shown which illustrate the method for defining and determining the maximum slope intensity disclosed herein. Figure 4B , 4D and 4F are close-ups of Figure 4A , 4C and 4E respectively, where the curves have their maximum intensity. The maximum intensity of the curve is indicated by an asterisk in Figure 4B , by a square in Figure 4D and 4F , and the maximum slope intensity is indicated by a diamond in the figure. The maximum slope intensity is defined as the intensity value at the time point where the distance to the perfusion slope exceeds a predefined limit, e.g., a limit based on a constant (k2) multiplied by the standard deviation of the perfusion slope. As shown in FIG. 4, there may be significant differences in time and intensity between the maximum intensity and the maximum slope intensity of the curve. The slope rise time can be defined as the difference between the peak (maximum) intensity of the curve and the slope starting point. However, as shown here, the slope rise time defined as the difference between the maximum slope intensity and the slope starting point gives a more relevant definition of the slope rise time.

[0227] Figures 5A - 5F Three embodiments are shown which illustrate the method for analyzing the washout of a fluorescent contrast agent disclosed herein. The intensity curves are the same as those in FIG. 4. Figure 5B , 5D and 5F are close-ups of Figure 5A , 5C and 5E respectively, where ICG is washed out. In the left figure, the maximum intensity is indicated by an asterisk in Figure 5A , by a square in Figure 5C and 5EIn the figure, it is represented by a square. A close-up of the elution part is shown in the figure on the right. The elution data has been analyzed in the same way as the perfusion slope, and all possible elution slopes have been calculated. Similar to the determination of the perfusion slope in the above example, the elution slopes can be binned and classified in a histogram (not shown) to select the elution slope with the highest frequency. The elution start point is usually after the maximum intensity of the curve. In this embodiment, the elution start point is defined to be symmetric about the maximum curve intensity and the maximum slope intensity. In this embodiment, the elution end point is determined in the same way as the determination of the maximum slope intensity in the above example, that is, when the intensity differs from the elution slope by a predefined constant multiplied by the standard deviation of the elution slope.

[0228] Figures 6A - 6D Two additional fluorescence measurements using ICG are shown, illustrating the robustness of the analysis method disclosed in the present application. Figure 6A The first figure represented by... shows the intensity data, the slope start point, the calculated perfusion slope (dashed line), the maximum slope intensity, and the maximum curve intensity. The right figure shows a histogram of the binned perfusion slope data. It can be seen that the intensity data is not as stable as the other intensity curves disclosed herein, having many local variations and no obvious intensity decrease after the perfusion slope. There will be elution of ICG molecules, but the data shown here does not include this part. Figure 6A and 6B shows that the exemplary method disclosed herein is a very robust procedure that can be used to automatically and real-time determine the perfusion slope and other perfusion parameters derived therefrom. Figure 6A A large difference between the time points of the maximum slope intensity and the maximum curve intensity is also shown. The slope rise time derived from the maximum slope intensity is regarded as a more relevant parameter characterizing the passage of the ICG bolus.

[0229] In Figure 6C The second figure represented by... also shows unstable intensity data, and all the calculated perfusion slopes are distributed in a relatively large range, as shown in the corresponding histogram in Figure 6D However, by selecting the histogram bin with the highest frequency, relevant and accurate perfusion slope parameters can still be extracted from the data, thus providing another embodiment of the robustness of the method disclosed in the present application.

[0230] Figure 7Shows an output video frame of a video sequence obtained during intestinal surgery. The original video (i.e., one frame) of the surgery obtained during the passage of the ICG bolus is shown in the upper right corner. The same video frame after image processing is shown in the upper left corner, and tissue perfusion can now be seen more clearly. As indicated in the figure, four regions of interest (1, 2, 3, 4) are indicated in the video frame. The following figure shows the mean pixel intensity of the four regions of interest, plotted as a function of time (seconds) relative to the normalized intensity. The perfusion slopes of the four ROIs (1, 2, 3, 4) are calculated and shown as straight lines in the figure.

[0231] When only observing the two video frames above, it is impossible for the surgeon to determine whether all of the ROIs 1, 2, and 3 are perfused equally and sufficiently. For example, whether regions 1, 2, and 3 are equally suitable for anastomosis. After about 70 seconds, this can also be seen in the following figure, where the pixel intensities of ROIs 1, 2, and 3 are similar. However, by applying the method disclosed herein for determining the perfusion slopes of different ROIs, objective perfusion measurements can be immediately provided to the surgeon. In Figure 7 the embodiment, it can be seen from the calculated perfusion slopes that the perfusion of ROI 3 is reduced compared to ROI 1 and ROI 2. This information provides the surgeon with objective perfusion parameters as a basis for their surgical decisions, thereby ultimately increasing the chance of success of the surgical outcome.

[0232] Figure 8A Shows a still image of a normal video sequence obtained before resection of a patient's intestine. The image shows the small intestine (lower part) and the colon (upper part). It is the colon that is about to be resected, but by including the small intestine in the image analysis, other, potentially unbiased high-perfusion reference measurements of the patient's perfusion can be provided for comparison with later perfusion measurements.

[0233] Figure 8B Shows Figure 8A substantially the same subpart of the gastrointestinal tract as in

[0234] Figure 9A Shows at Figure 8BThe intensity curves obtained from the ROI and the perfusion slopes calculated according to the method disclosed herein, i.e., the perfusion slopes of the colon and small intestine before resection. Although the intensity curves look very different, the calculated perfusion slopes of the colon and small intestine are comparable. However, the perfusion slope of the small intestine is steeper (higher perfusion level) than that of the colon. This is also summarized in Figure 9B where the perfusion slopes of the small intestine (left) and colon (right) have been normalized with respect to the perfusion slope of the small intestine.

[0235] Figure 10A shows the same sub - part of the gastrointestinal tract as Figure 8A but a normal image obtained after resection of the intestine and before anastomosis. This is a crucial part of the surgery where the surgeon must evaluate whether the perfusion at both ends of the intestine remaining after resection is sufficient for anastomosis, or whether more intestine must be resected to ensure that the anastomosis is formed in an area of optimal perfusion, ultimately increasing the chances of a successful outcome. Therefore, the surgeon is interested in obtaining measurements of the perfusion in various regions surrounding the resected intestine. The small intestine is marked at the bottom of the image and the resected intestine (colon) is marked at the top of the image.

[0236] Figure 10B is a fluorescence image corresponding to the image in Figure 10A after injection of an ICG bolus. Five ROIs are shown in the image: one on the small intestine (red) as a high - perfusion reference, one at the reference position in the image (black) with essentially no blood perfusion (no / low - perfusion reference) and three (blue, green, and yellow) on the resected intestine (colon).

[0237] Figure 11A shows the intensity curves measured by Figure 10A and 10B . The red ROI corresponds to the small intestine, giving the steepest perfusion slope, and the black reference ROI naturally gives the lowest perfusion slope. The blue, green, and yellow ROIs corresponding to the three ROIs on the intestine provide comparable perfusion slopes, which are also summarized in Figure 11B where the perfusion slope of the small intestine (left, red) and the intestine (right, blue, green, and yellow) have been normalized with respect to the perfusion slope of the small intestine. There are significant differences compared to Figure 9B . In Figure 9B (before resection), the perfusion in the intestine is comparable to that in the small intestine, while after resection, the perfusion in the resected intestine is much lower than that in the small intestine. Further note that when comparing Figure 9A (before resection) with Figure 11A (after resection), the absolute value of the perfusion slope after resection is much larger, and this is also the case for the small intestine. This indicates that the absolute value of the perfusion slope (and other perfusion parameters) is less important than the relative value, as also shown in Figure 9B and 11BAs demonstrated in [reference]. That is, it is important to have one or more reference ROIs in image analysis so that the calculated perfusion parameters can be compared with corresponding perfusion parameters obtained from the same video clip. In this embodiment, the method for determining perfusion disclosed herein detects a significant decrease in the perfusion of the intestine (colon) relative to the perfusion of the small intestine. This important information can guide the surgeon in selecting the optimal location for anastomosis.

[0238] Figure 12A Actual measurement data from a human subject is shown. An ICG micro-injectant is repeatedly injected into the human subject at regular intervals (about 2 minutes in this embodiment). The time-intensity curve shows a pattern that is essentially sinusoidal and increases linearly with time. The increase in intensity over time is related to the ratio between the fluorophore dose and the washout time, during which the fluorescence intensity decreases. At a certain time point, approximately t = 3800 s, Figure 12B , perfusion is restricted, resulting in an ischemic episode, which can be seen by the lack of oscillations after this time point, forming a pattern that can be described as an ischemic plateau.

[0239] Figure 12C Idealized data showing a time-intensity sine curve is shown. After injection of the fluorescence imaging agent, the measured ROI intensity increases and then decreases during the washout phase. At approximately t = 3750 s, due to the onset of an ischemic condition, the measured data shows a fixed measured ROI intensity value. Alternatively, if there is no ischemic condition, it is expected that the measured values follow the dashed line so that the measured ROI values continuously follow the sine curve pattern.

[0240] Figure 12DIllustrated is idealized data showing a time-intensity sine curve in the absence of an ischemic condition, where the anatomical region of interest drifts in and out of focus. If the ROI is continuously observable, the dashed line shows the expected measurements. If this is not possible, for example due to the anatomical region of interest drifting in and out of the focus of the recorded image, the measured data may be incomplete and there may instead be gaps - time intervals in which measurement data for the anatomical region of interest are not obtained. Thus, even if the recorded data is incomplete, the system preferably is able to identify the sine pattern. If the system can correctly identify the sine pattern, it can be provided with the expected intensity value of the ROI at each time point, which can then be used for comparison with the measured value. If the (one or more) measured values differ from the (one or more) expected values, the system can be configured to provide an alert to the surgeon. Thus, the system can be configured such that it identifies the phase of the oscillatory / sine pattern of the measured time point or interval, which is thereafter compared with the expected phase for that time point or interval, where the expected phase is preferably based on the identified oscillatory pattern of repeated bolus injections and / or a known frequency. As a result, the system does not necessarily require continuous measured values, but can instead combine the time information of the measured time point or interval based on the expected phase of the oscillatory pattern such that a particular phase of the expected oscillatory pattern appears in the measured interval.

[0241] Figure 13A Illustrated are fluorescence intensity measurements of a human subject taken over a relatively long time interval (about 40 minutes), during which the human subject was repeatedly injected with an ICG micro-bolus. The intensity of seven individual ROIs was measured and assigned a separate color in the figure. The measured fluorescence intensity shows a periodic sine pattern, where the frequency is consistent with the injection frequency (about 120 s). Since the injection time is relatively short compared to the dose size, the pattern is a substantially linear increase due to the accumulation of the fluorescence imaging agent. At approximately t = 2000 s, the repeated injection of the fluorescence imaging agent is stopped, resulting in an approximately exponential decay of the fluorescence intensity.

[0242] Figure 13B Illustrated is Figure 13A an enlarged view of the marked region in. Here, less fluctuation can be seen within the same ROI as well as between different ROIs. At the same time, the cyclic intensity patterns are different and the patterns for each ROI have the same period.

[0243] Figure 13CShows a time-intensity plot of measurements taken on a human subject by repeated injection of a fluorescent imaging agent microbolus. The plot shows the results of venous occlusion, where between approximately t = 62 - 78 minutes, perfusion was restricted, although not completely blocked. In this case, the oscillatory dynamics of the measured fluorescence intensity stopped, and the measurements during venous occlusion showed an irregular increase. Thus, it should be noted that reduced perfusion does not necessarily result in a flat line, as is otherwise typically obtained during ischemic conditions.

[0244] References

[0245] References

[0246] [1] C. Toens et al.: Validation of IC-VIEW fluorescence videography in rabbit model of mesentereic ischaemia and reperfusion. Int J Colorectal Dis 2006; 21: 332 - 338.

[0247] [2] N. Nerup et al.: Quantification of fluorescence angiography in a porcine model. Langenbecks Arch Surg, web-published 15.11.2016.

[0248] [3] L. Boni et al.: Indocyanine green-enhanced fluorescence to assess bowel perfusion during laparoscopic colorectal resection. Surg Endosc (2016) 30: 2736–2742

[0249] [4] R. Uitert et al.: A stable optic-flow based method for tracking colonoscopy images. Conference Paper, July 2008

[0250] [5] US2016 / 262638

[0251] [6]D. Stein et al.: Colon Resection. http: / / emedicine.medscape.com / article / 1891505-overview, September 2015

[0252] Item

[0253] 1. A method for automatically perfusing and evaluating the anatomical structure of a subject, the method comprising intravenously administering a first fluorescent imaging agent corresponding to a bolus dose of less than 0.01 mg ICG / kg body weight, acquiring and analyzing time-series fluorescence images of the tissue of the anatomical structure after injecting the first fluorescent imaging agent, and determining at least one perfusion parameter of the anatomical structure based on the analysis.

[0254] 2. The method according to Item 1, wherein the agent is injected by a controllable infusion pump.

[0255] 3. The method according to any one of the preceding Items, wherein the agent is injected in the form of a series of bolus doses, with a predefined time between subsequent bolus doses.

[0256] 4. The method according to any one of the preceding Items, wherein the fluorescence emission of the anatomical structure is measured after each bolus dose injection.

[0257] 5. The method according to any one of the preceding Items, wherein the bolus dose comprises an increasing or decreasing amount of the reagent.

[0258] 6. The method according to Item 5, wherein the amount increases or decreases from one bolus dose to the subsequent bolus dose in 10% increments.

[0259] 7. The method according to any one of the preceding Items, wherein the minimum bolus dose is determined after administering a series of increasing or decreasing bolus doses, and the minimum bolus dose provides a quantifiable fluorescence emission representative of the perfusion of the anatomical structure.

[0260] 8. The method according to any one of the preceding Items, wherein the interval between bolus doses is between 5 and 600 seconds, such as between 15 and 300 seconds, such as between 45 and 210 seconds, such as between 90 and 120 seconds.

[0261] 9. The method according to any one of the preceding Items, wherein the interval between bolus doses is long enough to allow measurement of the perfusion slope of each bolus dose in the anatomical structure, and preferably, wherein the perfusion slope includes a slope start point and an elution slope.

[0262] 10. The method according to any one of the preceding items, wherein an isotonic solution (such as saline) of a certain volume is injected immediately after injecting the fluorescent imaging agent of the bolus, for example, wherein the volume is 1 - 20 mL, for example 2.5 - 15 mL, for example 5 - 10 mL.

[0263] 11. The method according to any one of the preceding items, wherein the amount of the fluorescent imaging agent corresponds to 0.0001 to 0.01 mg ICG / kg body weight per bolus, for example 0.0001 to 0.01 mg ICG / kg body weight per bolus.

[0264] 12. The method according to any one of the preceding items, wherein the initial amount of the fluorescent imaging agent corresponds to at least 0.001 mg ICG / kg body weight.

[0265] 13. The method according to item 12, wherein the subsequent bolus increases or decreases from one bolus to the subsequent bolus corresponding to at least 0.001 mg ICG / kg body weight.

[0266] 14. The method according to any one of the preceding items, wherein the bolus has a liquid volume of 0.5 μL to 10 mL, for example 0.5 - 5 mL.

[0267] 15. The method according to any one of the preceding items, wherein a second fluorescent imaging agent is administered, and the emission maximum of the second fluorescent imaging agent differs from the emission maximum of the first fluorescent imaging agent by at least 50 nm.

[0268] 16. The method according to any one of the preceding items, wherein a third, fourth, fifth or more fluorescent imaging agents are administered.

[0269] 17. The method according to item 15 or 16, wherein the first fluorescent imaging agent and the subsequent fluorescent imaging agents are administered alternately.

[0270] 18. The method according to item 15, 16 or 17, wherein the interval between the administrations of different fluorescent imaging agents is half of the interval between the subsequent administrations of the same fluorescent imaging agent.

[0271] 19. The method according to any one of the preceding items, wherein the fluorescence is automatically detected by irradiating the anatomical structure with a light source capable of exciting the fluorescent imaging agent, and the emission is quantified by a series of fluorescence images of the anatomical structure.

[0272] 20. The method according to any one of the preceding items, wherein the time period between boluses is determined by a computer configured to detect the perfusion slope caused by each bolus.

[0273] 21. The method according to any one of the preceding items, wherein the time period between the dose of the fluorescent imaging agent and / or the bolus is selected such that an oscillatory pattern of the time series of the average intensity of the ROI can be received.

[0274] 22. The method according to any one of the preceding items, wherein longer intervals are maintained at regular intervals, such as every 20 boluses, more preferably every 40 boluses, and most preferably every 60 boluses, for example at least 1 minute, so that the background fluorescence level can be reduced.

[0275] 23. The method according to any one of the preceding items, wherein the amount of the fluorescent imaging agent in the bolus is controlled by a computer configured to determine the minimum bolus that can determine the minimum fluorescence emission representative of the perfusion of the anatomical structure.

[0276] 24. The method according to any one of the preceding items, wherein the anatomical structure is the gastrointestinal tract, preferably including the buccal cavity; pharynx; small intestine, including the duodenum, jejunum, and ileum; stomach, including the esophagus, cardia, and pylorus; large intestine, including the cecum, colon, rectum, and anal canal.

[0277] 25. The method according to any one of the preceding items, wherein the anatomical structure is an internal organ of the subject.

[0278] 26. The method according to any one of the preceding items, wherein the anatomical structure is the skin of the subject.

[0279] 27. The method according to any one of the preceding items, wherein the anatomical structure includes a wound, which is the object of perfusion assessment.

[0280] 28. The method according to any one of the preceding items, wherein the fluorescent imaging agent comprises indocyanine green (ICG), fluorescein isothiocyanate, rhodamine, phycoerythrin, phycocyanin, allophycocyanin, o-phthalaldehyde, fluorescamine, rose bengal, trypan blue, fluorogold, green fluorescent protein, flavin, methylene blue, porphysome, cyanine dye, IRDye800CW, CLR 1502 conjugated with a targeting ligand, OTL38 conjugated with a targeting ligand, or a combination thereof.

[0281] 29. The method according to any one of the preceding items, further comprising the step of: tracking the movement of the anatomical structure in the video image.

[0282] 30. The method according to any one of the preceding items, further comprising the steps of: tracking the movement of at least a part of the anatomical structure in the video image, and correlating the movement such that at least the first region of interest corresponds to the same subpart of the anatomical structure in the video image.

[0283] 31. The method according to any one of the preceding items, wherein the motion tracking is provided by free image tracking.

[0284] 32. The method according to any one of the preceding items, wherein the motion tracking is provided in the form of classifier-based tracking by free image tracking, and the free image tracking includes the steps of: in the video image, preferably in at least one area adjacent to or surrounding a region of interest, determining a classifier for a plurality of recognizable features.

[0285] 33. The method according to any one of the preceding items, wherein the motion tracking is provided in the form of color-based tracking by free image tracking.

[0286] 34. The method according to any one of the preceding items, wherein the motion tracking is based on color tracking of one or more color markers applied to the gastrointestinal tract.

[0287] 35. The method according to any one of the preceding items, wherein the motion tracking includes the steps of: color filtering and thresholding to obtain a boolean map of the pixels in the video image.

[0288] 36. The method according to any one of the preceding items, further comprising the step of: noise filtering to improve the boolean map.

[0289] 37. The method according to any one of the preceding items, wherein the motion tracking is provided by object-based tracking.

[0290] 38. The method according to any one of the preceding items, wherein the motion tracking is provided by tracking the motion of one or more predefined objects attached to the anatomical structure.

[0291] 39. The method according to any one of the preceding items, which includes the steps of: creating a ROI template by initially storing an image of each ROI, and wherein the motion tracking is provided by applying cross-correlation to each ROI template.

[0292] 40. The method according to any one of the preceding items, wherein the tracking is performed such that three-dimensional information of at least a part of the anatomical structure is acquired.

[0293] 41. The method according to any one of the preceding items, wherein the perfusion assessment includes determining the location of perfusion complications in the anatomical structure.

[0294] 42. The method according to any one of the preceding items, wherein the perfusion assessment is used in combination with a diagnostic or surgical procedure.

[0295] 43. The method according to item 42, wherein the procedures include diagnostic laparoscopy, exploratory laparoscopy, surgical laparoscopy and conventional laparoscopy, robotic surgery, and open surgery.

[0296] 44. The method according to item 42, wherein the procedures include anastomosis, such as intestinal anastomosis.

[0297] 45. A fluorescence imaging agent for use in the method according to any one of the preceding items.

[0298] 46. Use of a fluorescence imaging agent in the preparation of a medicament for an automated perfusion assessment method according to any one of the preceding items 1 - 44.

[0299] 47. A system for automated perfusion assessment of an anatomical structure during a medical procedure on a subject, comprising a controllable injection pump for containing at least one first fluorescence imaging agent, the injection pump being configured to inject a predefined amount of the first fluorescence imaging agent into the blood of the subject, wherein the system is configured to receive and analyze time - series fluorescence images of the tissue of the anatomical structure after injection of the first fluorescence imaging agent, and to determine at least one perfusion parameter of the anatomical structure based on the analysis.

[0300] 48. The system according to any one of the preceding items, wherein the system is configured to control the injection pump to inject an initial small bolus of the fluorescence imaging agent, preferably in an amount corresponding to less than 0.01 mg ICG / kg body weight, and subsequently analyze the fluorescence emission generated by the initial bolus.

[0301] 49. The system according to any one of the preceding items, wherein the system is configured to control the injection pump to inject an initial small bolus of the fluorescence imaging agent, preferably in an amount corresponding to less than 1 mg ICG or less than 0.8 mg ICG or less than 0.6 mg ICG or less than 0.4 mg ICG or less than 0.2 mg ICG, and subsequently analyze the fluorescence emission generated by the initial bolus.

[0302] 50. The system according to any one of the preceding items, wherein the system is configured to determine a subject - specific minimum effective bolus of the fluorescence imaging agent by the following steps:

[0303] - Controlling the injection pump to inject a series of boluses of the fluorescence imaging agent in predefined increasing or decreasing amounts, with a predefined time period between each bolus,

[0304] - Analyzing the fluorescence emission of the anatomical structure after injection of each bolus, and

[0305] - Determining the size of the minimum bolus that provides quantifiable fluorescence emission from the anatomical structure.

[0306] 51. The system according to any one of the preceding items, wherein the system is configured to: 1) receive time series images of the tissue of the anatomical structure before injecting the fluorescent agent; and 2) thereby determine the background noise level.

[0307] 52. The system according to any one of the preceding items, wherein the system is configured to determine a subject-specific conversion period, the subject-specific conversion period being defined as the time period from the bolus injection of the fluorescent imaging agent to the increase in the fluorescence slope in the fluorescence emission.

[0308] 53. The system according to any one of the preceding items, wherein the system is configured to determine a subject-specific interruption interval, the subject-specific interruption interval being defined as the time period from the rise in the fluorescence slope to the fluorescence emission being equal to the background noise.

[0309] 54. The system according to any one of the preceding items, wherein the system is configured to automatically: 1) control an injection pump to inject a series of boluses of a predefined fluorescent imaging agent, a predefined bolus such as a minimum effective bolus, and to space a predefined duration between each bolus, and 2) determine at least one perfusion parameter of the anatomical structure after injecting each bolus.

[0310] 55. The system according to any one of the preceding items, wherein the system is configured to determine the at least one perfusion parameter in one or more regions of interest located in the anatomical structure and optionally in adjacent anatomical structures.

[0311] 56. The system according to any one of the preceding items, wherein the system is configured to automatically: 1) control an injection pump to inject a series of boluses of a fluorescent imaging agent in an increasing or decreasing amount, spacing a predefined time period between each bolus; and 2) determine at least one perfusion parameter of the anatomical structure after injecting each bolus.

[0312] 57. The system according to any one of the preceding items, comprising at least a second controllable injection pump for containing at least a second fluorescent agent, the second fluorescent agent being different from the first fluorescent agent, the second injection pump being configured to inject a predefined amount of the second fluorescent imaging agent into the blood of a subject.

[0313] 58. The system according to any one of the preceding items, wherein the system is configured to determine the at least one perfusion parameter in one or more regions of interest located in the anatomical structure and optionally in adjacent anatomical structures.

[0314] 59. The system according to any one of the preceding items 58 is configured such that the region of interest can be selected by a user of the system.

[0315] 60. The system according to any one of the preceding items further comprises at least one light source configured to provide excitation light to induce fluorescence emission from the first and / or second fluorophore in the anatomical structure.

[0316] 61. The system according to any one of the preceding items further comprises: an imaging unit configured to record at least one time series of fluorescence emission from the anatomical structure.

[0317] 62. The system according to any one of the preceding items, wherein the imaging unit is configured for white light imaging.

[0318] 63. The system according to any one of the preceding items is configured to send the at least one perfusion parameter for presentation on a display.

[0319] 64. The system according to any one of the preceding items, wherein the anatomical structure is the gastrointestinal tract, preferably including the buccal cavity; pharynx; small intestine, including the duodenum, jejunum and ileum; stomach, including the esophagus, cardia and pylorus; large intestine including the cecum, colon, rectum and anal canal.

[0320] 65. The system according to any one of the preceding items, wherein the anatomical structure is an internal organ of a subject.

[0321] 66. The system according to any one of the preceding items, wherein the anatomical structure is the skin of a subject.

[0322] 67. The system according to any one of the preceding items, wherein the anatomical structure includes a wound, and the subject is for perfusion assessment.

[0323] 68. The system according to any one of the preceding items, wherein the system is part of a laparoscopic setup, and the imaging unit and the light source are incorporated into the laparoscopic unit.

[0324] 69. The system according to any one of the preceding items, wherein the system is part of an open surgical setup, and the imaging unit and the light source are incorporated into the open surgical unit.

[0325] 70. The system according to any one of the preceding items, wherein the fluorescent imaging agent comprises indocyanine green (ICG), fluorescein isothiocyanate, rhodamine, phycoerythrin, phycocyanin, allophycocyanin, o-phthalaldehyde, fluorescamine, rose bengal, trypan blue, Fluoro-Gold, green fluorescent protein, flavin, methylene blue, porphyrin liposome, cyanine dye, IRDye800CW, CLR 1502 conjugated with a targeting ligand, OTL38 conjugated with a targeting ligand, or a combination thereof.

[0326] 71. The system according to any one of the preceding items, wherein the system is configured to evaluate the drainage area of a vein or a group of veins, lymphatic vessels, lymph nodes, or other parts of the circulatory and / or lymphatic pathways.

[0327] 72. The system according to any one of the preceding items, which is configured to perform the method according to any one of items 1-44.

[0328] 73. A computer-implemented method for detecting perfusion changes in at least a portion of an anatomical structure, wherein a repeatable bolus containing a fluorescent imaging agent is continuously injected into a subject; the method comprises the following steps:

[0329] i. Measuring the time-series fluorescence intensity of a region of interest of at least a portion of the anatomical structure;

[0330] ii. Identifying the measurement pattern of the measured time series,

[0331] iii. Based on the measurement pattern, creating an expected pattern, where the fluorescence intensity of at least a portion of the anatomical structure of interest is expected to follow the expected pattern;

[0332] iv. Measuring the fluorescence intensity of the anatomical region of interest;

[0333] v. Analyzing the difference between the expected pattern and the measured values; and

[0334] vi. Repeating steps iv. and v. to continuously evaluate the perfusion of at least a portion of the anatomical region of interest.

[0335] 74. The computer-implemented method according to item 73, wherein an alert is issued to the user based on the difference between the expected pattern and the measured values according to a predefined function such as a predefined threshold.

[0336] 75. The computer-implemented method according to any one of items 73-74, wherein the identified oscillation pattern is continuously updated between steps iv. and v.

[0337] 76. The computer-implemented method according to any one of items 73-75, wherein the oscillation pattern is identified based on frequency, amplitude, phase, and / or background intensity.

[0338] 77. The computer-implemented method according to any one of items 73 - 76, wherein the bolus is substantially the minimum effective bolus.

[0339] 78. The computer-implemented method according to any one of items 73 - 77, wherein injection parameters such as injection frequency are additionally or alternatively used to identify the oscillation pattern.

[0340] 79. The computer-implemented method according to any one of items 73 - 78, wherein the method is used to predict the onset of an ischemic condition.

[0341] 80. The computer-implemented method according to any one of items 73 - 79, wherein the anatomical region of interest is detected by tracking.

[0342] 81. The computer-implemented method according to any one of items 73 - 80, wherein the tracking of the anatomical region of interest is performed in three dimensions.

[0343] 82. The computer-implemented method according to any one of items 73 - 81, wherein the bolus is injected over a longer time period, for example between 1 and 5 minutes, more preferably between 1 and 4 minutes, even more preferably between 1 and 3 minutes, and most preferably between 1.5 and 2.5 minutes.

[0344] 83. The computer-implemented method according to any one of items 73 - 82, wherein periodically, for example after every 10 - 300 boluses, more preferably after every 30 - 300 boluses, more preferably after every 90 - 300 boluses, and most preferably after every 200 - 300 boluses, a longer pause is made, for example between 1 - 10 minutes, during which no fluorescent imaging agent is injected into the subject.

[0345] 84. The computer-implemented method according to any one of items 73 - 83, wherein an alert is issued to the user based on the difference between the measured values of phase, frequency, and / or amplitude and the expected values.

[0346] 85. The computer-implemented method according to any one of items 73 - 84, wherein the method is capable of detecting ischemia and / or venous occlusion and / or evaluating the perfusion area of an artery.

[0347] 86. The computer-implemented method according to any one of items 73 - 85, wherein the method is configured to compensate for measurements at non-consecutive intervals, for example when the region of interest drifts in and out of focus, and compare these with the expected pattern.

[0348] 87. A computer-implemented method for detecting perfusion changes in a region of interest of a subject by hemodynamics in at least a portion of the region of interest of the subject obtained from a video image by image processing, the method comprising the steps of:

[0349] - Performing image analysis on at least one video sequence obtained during and / or after applying a plurality of bolus agents containing a fluorescent imaging agent to the subject, wherein the plurality of bolus agents are supplied according to a predefined pattern, for example in terms of frequency and / or dose.

[0350] - Calculating subsequent perfusion parameters for one or more regions of interest based on the image analysis, and

[0351] - Monitoring the subsequent perfusion parameters to determine changes in perfusion in the region of interest.

[0352] 88. The method according to item 87, comprising the steps according to any one of items 1-46 or items 73-86.

Claims

1. A system for automatically perfusing an anatomical structure during a medical procedure on a subject, the system comprising a processing unit and a controllable injection pump for containing at least one first fluorescent imaging agent, wherein the system is configured to: - Control the injection pump to automatically inject a series of predefined boluses of the first fluorescent imaging agent into a vein of the subject in a series of at least three boluses, with a predefined duration between each bolus ranging from 30 to 600 seconds, each bolus containing a quantity of the first fluorescent imaging agent, wherein the quantity of the first fluorescent imaging agent is dissolved in a liquid, and the first fluorescent imaging agent has an emission maximum. - Receive and analyze time series fluorescence images of the tissue of the anatomical structure through the processing unit after each of at least three boluses of the first fluorescent imaging agent is administered. - Determine, through the processing unit, at least one perfusion parameter of the anatomical structure based on the analysis after each bolus of the first fluorescent imaging agent is injected.

2. The system according to claim 1, wherein, The duration between each bolus ranges from 15 to 300 seconds.

3. The system according to claim 1, wherein The duration between each bolus ranges from 45 to 210 seconds.

4. The system according to claim 1, wherein The duration between each bolus ranges from 90 to 120 seconds.

5. A method for automatically perfusing an anatomical structure of a subject, executed by a processing unit, the method comprising: - Obtaining and analyzing time series fluorescence images of the tissue of the anatomical structure after each bolus of a series of at least 3 boluses of a first fluorescent imaging agent is administered into a vein, the first fluorescent imaging agent having an emission maximum, with a predefined duration between the administration of each bolus ranging from 30 to 600 seconds, each bolus containing a quantity of the first fluorescent imaging agent, wherein the quantity of the first fluorescent imaging agent is dissolved in a liquid. - Determining at least one perfusion parameter of the anatomical structure based on each of the analyses.

6. The method according to claim 5, wherein the first fluorescent imaging agent is injected through a controllable injection pump.

7. The method according to claim 5, wherein the fluorescence emission of the anatomical structure is measured after each bolus injection.

8. The method according to claim 5, wherein the bolus comprises an increasing or decreasing quantity of the first fluorescent imaging agent.

9. The method according to claim 8, wherein the quantity increases or decreases from one bolus to the subsequent bolus at 10% intervals.

10. The method according to claim 5, wherein a minimum bolus is determined after a series of increasing or decreasing boluses are administered, and the minimum bolus provides a quantifiable fluorescence emission representative of the perfusion of the anatomical structure.

11. The method according to claim 5, wherein The predefined duration between each bolus ranges from 15 to 300 seconds.

12. The method according to claim 5, wherein, The predefined duration between each bolus ranges from 45 to 210 seconds.

13. The method according to claim 5, wherein, The predefined duration between each bolus ranges from 90 to 120 seconds.

14. The method according to claim 5, wherein each bolus has a liquid volume of 0.5 μL to 10 mL or 0.5 - 5 mL.

15. The method according to claim 5, wherein a second fluorescent imaging agent is administered, and the emission maximum of the second fluorescent imaging agent differs from the emission maximum of the first fluorescent imaging agent by at least 50 nm.

16. The method according to claim 5, wherein the anatomical structure is the gastrointestinal tract, including the buccal cavity; pharynx; small intestine, including the duodenum, jejunum, and ileum; stomach, including the esophagus, cardia, and pylorus; large intestine, including the cecum, colon, rectum, and anal canal.

17. The method according to claim 5, wherein the anatomical structure is an internal organ of the subject, wherein the anatomical structure is the skin of the subject, or wherein the anatomical structure includes a wound, which is the subject of perfusion assessment.

18. The method according to claim 5, wherein the fluorescent imaging agent comprises indocyanine green (ICG), fluorescein isothiocyanate, rhodamine, phycoerythrin, phycocyanin, allophycocyanin, o-phthalaldehyde, fluorescamine, rose bengal, trypan blue, Fluoro-Gold, green fluorescent protein, flavin, methylene blue, porphyrin liposomes, cyanine dyes, IRDye800CW, CLR 1502 conjugated to a targeting ligand, OTL38 conjugated to a targeting ligand, or a combination thereof.

19. The method according to claim 5, wherein the perfusion assessment includes determining the location of perfusion complications in the anatomical structure.

Images